Flare Spectra Research Articles

Exploring plasma evolution during Sagittarius A* flares

We present a new way of describing the flares from Sgr A* with a self-consistent calculation of the particle distribution. All relevant radiative processes are taken into account in the evolution of the electron distribution and resulting spectrum. We present spectral modelling for new X-ray flares observed by NuSTAR, together with older observations in different wavelengths, and discuss the changes in plasma parameters to produce a flare. We show that under certain conditions, the real particle distribution can differ significantly from standard distributions assumed in most studies. We conclude that the flares are likely generated by magnetized plasma consistent with our understanding of the accretion flow. Including non-thermal acceleration, injection, escape, and cooling losses produces a spectrum with a break between the infrared and the X-ray, allowing a better simultaneous description of the different wavelengths. We favour the non-thermal synchrotron interpretation, assuming the infrared flare spectrum used is representative. We also consider the effects on Sgr A*'s quiescent spectrum in the case of a density increase due to the G2 encounter with Sgr A*.

MP15-15 SYMPTOM VARIABILITY AND ITS IMPACT AMONG FEMALE INTERSTITIAL CYSTITIS/BLADDER PAIN SYNDROME PATIENTS IN THE MAPP NETWORK: AN IN-DEPTH QUALITATIVE ANALYSIS

INTRODUCTION AND OBJECTIVES: Although in-depth qualitative information is critical for understanding symptom variability and its impact, no previous qualitative studies have described interstitial cystitis/bladder pain syndrome (IC/BPS) symptom variability, particularly symptom exacerbations referred to commonly as “flares”. METHODS: We conducted a series of eight focus groups of female IC/BPS patients at four sites of the Multidisciplinary Approaches to the study of chronic Pelvic Pain (MAPP) research network to describe the full spectrum of flares and to explore their impact on patients’ quality of life. Each focus group consisted of a 1.5 hour discussion moderated by the same female moderator. Focus groups were recorded, transcribed verbatim, and coded by one rater with a comprehensive set of 122 descriptive codes using Atlas-ti. A 20% sample of quotes was re-coded by a separate rater with high reproducibility (mean kappa1⁄40.91). RESULTS: 57 female IC/BPS patients participated in the focus groups (mean1⁄47/group), almost all of whom reported symptom exacerbations. Most participants referred to these exacerbations as “flares” or derivations thereof, whereas a smaller proportion used phrases such as “bad bladder days.” Reported flares varied widely in terms of symptoms (pelvic pain, urgency, frequency, and concurrent extra-pelvic pain, irritable bowel symptoms, etc); symptom intensity (“dull pressure” to “so painful that I want to die”); duration (minutes to one year) and frequency (daily to rarely), although the most commonly described flares were painful, days-long flares. The impact of flares also varied widely. Some participants reported no major short-term impact during flares, whereas others reported major disruption to their work and other activities. Some participants also described longer-term impact, including loss of employment or limited career advancement; reduced travel and social activities, and negative effects on their sexual functioning and marital, family, and social relationships. CONCLUSIONS: Our findings suggest a wide spectrum of flare experiences and major immediate and long-term impact of flares. Future research should focus on ways in which to prevent and treat this bothersome aspect of IC/BPS.

A solar flare simulation and dosimetry facility at a proton therapy cyclotron

During extravehicular activities (EVA) astronauts are exposed to intense radiation from solar flare events (SFE). Hence, the radiation shielding efficacy of space suits, in particular the helmets and extra vehicular visor assembly (EVVA) are imperative to safety of astronauts and ultimate success of the space mission. At West German Proton Therapy Centre Essen (WPE) we have replicated the historical solar flare spectra by manipulating the treatment planning system (TPS) of the 230 MeV proton-therapy cyclotron and developed novel proton irradiation and dosimetry methods for the testing of space borne devices as mentioned above. We have used a single foil of radiochromic film (type EBT 2) to estimate the proton depth dose distribution in the human eye. The optimal thickness of EVVA (acryl glass) for the protection from solar flares was estimated to be 2.35 cm. A maximum SFE proton dose up to 20 Gy found to be well assessed using the EBT 2 films.

Intraoperative fluorescence delineation of head and neck cancer with a fluorescent Anti‐epidermal growth factor receptor nanobody

Intraoperative near-infrared (NIR) fluorescence imaging is a technology with high potential to provide the surgeon with real-time visualization of tumors during surgery. Our study explores the feasibility for clinical translation of an epidermal growth factor receptor (EGFR)-targeting nanobody for intraoperative imaging and resection of orthotopic tongue tumors and cervical lymph node metastases. The anti-EGFR nanobody 7D12 and the negative control nanobody R2 were conjugated to the NIR fluorophore IRDye800CW (7D12-800CW and R2-800CW). Orthotopic tongue tumors were induced in nude mice using the OSC-19-luc2-cGFP cell line. Tumor-bearing mice were injected with 25 µg 7D12-800CW, R2-800CW or 11 µg 800CW. Subsequently, other mice were injected with 50 or 75 µg of 7D12-800CW. The FLARE imaging system and the IVIS spectrum were used to identify, delineate and resect the primary tumor and cervical lymph node metastases. All tumors could be clearly identified using 7D12-800CW. A significantly higher tumor-to-background ratio (TBR) was observed in mice injected with 7D12-800CW compared to mice injected with R2-800CW and 800CW. The highest average TBR (2.00 ± 0.34 and 2.72 ± 0.17 for FLARE and IVIS spectrum, respectively) was observed 24 hr after administration of the EGFR-specific nanobody. After injection of 75 µg 7D12-800CW cervical lymph node metastases could be clearly detected. Orthotopic tongue tumors and cervical lymph node metastases in a mouse model were clearly identified intraoperatively using a recently developed fluorescent EGFR-targeting nanobody. Translation of this approach to the clinic would potentially improve the rate of radical surgical resections.

EXTREME ULTRAVIOLET SPECTRA OF SOLAR FLARES FROM THE EXTREME ULTRAVIOLET SPECTROHELIOGRAPH SPIRIT ONBOARD THE CORONAS-F SATELLITE

We present detailed EUV spectra of 4 large solar flares: M5.6, X1.3, X3.4, and X17 classes in the spectral ranges 176-207 \AA\ and 280-330 \AA. These spectra were obtained {by the slitless} spectroheliograph SPIRIT aboard the CORONAS-F satellite. To our knowledge these are the first detailed EUV spectra of large flares obtained with spectral resolution of $\sim 0.1$ \AA. We performed a comprehensive analysis of the obtained spectra and provide identification of the observed spectral lines. The identification was performed based {on the calculation} of synthetic spectra (CHIANTI database was used), with simultaneous {calculations of DEM} and density of the emitting plasma. More than 50 intense lines are present in the spectra that correspond to a temperature range of $T=0.5-16$ MK; most of the lines belong to Fe, Ni, Ca, Mg, Si ions. In all the considered flares intense hot lines from Ca XVII, Ca XVIII, Fe XX, Fe XXII, and Fe XXIV are observed. The calculated DEMs have a peak at $T \sim 10$ MK. The densities were determined using Fe XI - Fe XIII lines and averaged $6.5 \times 10^9$ cm$^{-3}$. We also discuss the identification, accuracy and major discrepancies of the spectral line intensity prediction.

Study of properties of cosmic rays and solar X-ray flares by balloon borne experiments

We are engaged in pioneering balloon borne experiments with typical payloads less than ~3.5 kg. Low cost rubber balloons are used to fly them to a height of about 40 km. In a double balloon system, the booster balloon lifts the orbiter balloon to its cruising altitude where data is taken for a longer period of time. In this paper, we present our first scientific report on the variation of cosmic rays and muons with altitude and detection of several solar flares in X-rays between 20 and 100 keV. We have found the altitude of the Pfotzer maximum at Tropic of Cancer for cosmic rays and muons and catch several solar flares in hard X-rays. We find that the hard X-ray (>40 keV) sky becomes very transparent above Pfotzer maximum. We find the flare spectrum to have a power-law distribution. From these studies, we infer that valuable scientific research could be carried out in near space using low cost balloon borne experiments.

The Risky Road to Mars

In their Report “Measurements of energetic particle radiation in transit to Mars on the Mars Science Laboratory” (31 May, p. [1080][1]), C. Zeitlin et al. try to assess the radiation risks to astronauts from exposure to galactic cosmic rays and solar flares during a manned expedition to Mars. They conclude that astronauts will receive about two-thirds of the lifetime exposure limit for humans during the round trip. I believe the dose could be even higher. ![Figure][2] Astronaut on Mars (artist's conception) CREDIT: DIETER SPEARS/INHAUS CREATIVE/ISTOCKPHOTOS Zeitlin et al. did not consider the secondary effects of radiation-induced nuclear reactions in the human body. Nuclear reactions of protons and alpha particles with carbon, nitrogen, and oxygen nuclei lead to formation of lithium, beryllium, and boron nuclei. These reactions are most likely to happen for incident protons and alphas with energies between 5 and 100 MeV, particularly those between 10 and 50 MeV ([ 1 ][3]). The lithium, beryllium, and boron nuclei produced in such reactions are low in energy and much more heavily ionizing (i.e., more dangerous) than higher-energy protons or alphas. Thus, this type of radiation, below 100 MeV, is most likely to produce significant damage in human tissue. This radiation comes not only from the primary flare and galactic cosmic ray fluxes studied by Zeitlin et al. , but also from the secondary flux of protons and alphas originating in the space capsule shielding, as well as from nuclear reactions. In the event of a significant solar flare event while an astronaut is outside the space capsule, the radiation effects would be further magnified, because the reaction probabilities are highest at energies corresponding to the solar flare spectrum. 1. [↵][4] 1. S. M. Read, 2. V. E. Viola , Atomic Data and Nuclear Data Tables 31, 359 (1984). [OpenUrl][5][CrossRef][6][Web of Science][7] [1]: /lookup/doi/10.1126/science.1235989 [2]: pending:yes [3]: #ref-1 [4]: #xref-ref-1-1 View reference 1 in text [5]: {openurl}?query=rft.jtitle%253DAtomic%2BData%2Band%2BNuclear%2BData%2BTables%26rft.volume%253D31%26rft.spage%253D359%26rft_id%253Dinfo%253Adoi%252F10.1016%252F0092-640X%252884%252990009-3%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [6]: /lookup/external-ref?access_num=10.1016/0092-640X(84)90009-3&link_type=DOI [7]: /lookup/external-ref?access_num=A1984ADL7000001&link_type=ISI

Robert Peichung Lin

Robert Peichung Lin died suddenly from a stroke on 17 November 2012 in Berkeley, California. His titanic career in experimental space science spanned 50 years. He was known especially for his innovative experimental concepts and was widely considered to be the father of modern experimental high-energy solar physics.Bob was born on 24 January 1942 in Kwangsi, China. During his childhood, his family moved first to London then to the US as his father established an academic career. In 1962 Bob graduated from Caltech with a physics degree and joined the physics graduate program at the University of California, Berkeley. He received his PhD in physics in 1967 with Kinsey Anderson as his research adviser and then joined the staff at Berkeley’s Space Sciences Laboratory (SSL). In 1991 he became a professor in the physics department at Berkeley; he served as director of SSL from 1998 to 2008; and in 2011 he retired from teaching. Apart from a sabbatical year at ETH Zürich, Bob spent his entire professional career at Berkeley. He remained fully active in research after his retirement from the classroom.When Bob arrived at Berkeley in 1962, Anderson’s group was operating a vigorous program of rocket- and balloon-borne x-ray measurements. Anderson had just made the first measurements of the x rays associated with solar flares and of the x-ray spectrum of the aurora. The group was just starting to develop instruments for satellite missions, and Bob recognized quickly the enormous potential for that work. For his PhD thesis, he used Geiger–Müller tube experiments developed at Berkeley to make measurements of the spectrum of interplanetary electrons generated by solar flares.In the early 1970s, Anderson and Bob convinced NASA to include a simple electron spectrometer on the lunar satellites launched by Apollo 15 and Apollo 16. Bob used the instruments to analyze the remnant magnetic fields in the lunar crust by measuring 10- to 1000-eV electrons reflected by those fields. Later, using follow-on instruments on the Lunar Prospector and the Mars Global Surveyor, he and his students mapped the crustal magnetic field of the Moon and Mars. The NASA MAVEN (Mars Atmosphere and Volatile Evolution) mission, scheduled to launch in November 2013, carries a full payload of in situ instruments inspired by Bob’s research on the interaction of the solar wind with Mars.Bob’s early work on solar-flare electrons led to instrument suites on the ISEE-3 (International Sun–Earth Explorer 3; 1978), Giotto (1986), Wind (1994), and STEREO (Solar Terrestrial Relations Observatory; 2006). Bob and his students and collaborators used those instruments to study energetic electrons and ions associated with solar flares, coronal mass ejections, magnetic reconnection, and other space-plasma phenomena. He and his collaborators made the first measurements of in situ plasma radio-emission processes, diagnosed the source regions for particle energization in solar flares, measured the helical magnetic field-line length inside a coronal mass ejection, and studied the interaction of Comet Halley with solar wind, among many other things.In the 1980s and 1990s, Bob’s group flew balloon payloads with solid-state germanium detectors and sodium iodide and cesium iodide scintillator detectors to study hard x-ray and gamma-ray spectra of solar flares. He used those experiments to discover a class of microflares and to separate the thermal and nonthermal emissions. Meanwhile, another group had developed a balloon-borne imaging system with rotating modulation collimators to study solar hard x rays and gamma rays. Bob worked tirelessly for years to marry the two technologies for a space mission; the result was NASA’s RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager), launched in 2002. Bob served as the NASA principal investigator and led the science team with great enthusiasm. The mission’s success and discoveries have led to the new instrument concepts currently being developed for and flown on sounding rocket flights and long-duration balloons.For NASA’s STEREO mission, Bob developed a simple solid-state particle detector, with a very good sensitivity to suprathermal particles, and found that the instrument was sensitive to energetic neutral particles created by charge exchange in Earth’s magnetosphere. That led to his final effort on energetic neutral spectroscopy: the development of a small microsatellite—CINEMA (CubeSat for Ions, Neutrals, Electrons, and Magnetic Fields)—to study Earth’s ring-current region.Most recently, Bob had professorial appointments at Kyung Hee University in South Korea and Peking University in China and had begun new collaborations with groups in both countries to develop space-instrumentation expertise.Bob was an inspiring and generous colleague and is remembered warmly by his students, postdocs, and collaborators. Throughout his career he received many professional honors, always with humility, but he was most at home at the Berkeley SSL or at his biweekly Chinese lunch with his friends and colleagues.Robert Peichung LinPEG SKORPINSKIPPT|High resolution© 2013 American Institute of Physics.

The energetic relationship among geoeffective solar flares, associated CMEs and SEPs

Major solar eruptions (flares, coronal mass ejections (CMEs) and solar energetic particles (SEPs)) strongly influence geospace and space weather. Currently, the mechanism of their influence on space weather is not well understood and requires a detailed study of the energetic relationship among these eruptive phenomena. From this perspective, we investigate 30 flares (observed by RHESSI), followed by weak to strong geomagnetic storms. Spectral analysis of these flares suggests a new power-law relationship (r ∼ 0.79) between the hard X-ray (HXR) spectral index (before flare-peak) and linear speed of the associated CME observed by LASCO/SOHO. For 12 flares which were followed by SEP enhancement near Earth, HXR and SEP spectral analysis reveals a new scaling law (r ∼ 0.9) between the hardest X-ray flare spectrum and the hardest SEP spectrum. Furthermore, a strong correlation is obtained between the linear speed of the CME and the hardest spectrum of the corresponding SEP event (r ∼ 0.96). We propose that the potentially geoeffective flare and associated CME and SEP are well-connected through a possible feedback mechanism, and should be regarded within the framework of a solar eruption. Owing to their space weather effects, these new results will help improve our current understanding of the Sun-Earth relationship, which is a major goal of research programs in heliophysics.

A low-level accretion flare during the quiescent state of the neutron-star X-ray transient SAX J1750.8−2900

We report on a series of Swift/X-ray telescope observations, performed between 2012 February and 22 March, during the quiescent state of the neutron-star X-ray binary SAX J1750.8−2900. In these observations, the source was either just detected or undetected, depending on the exposure length (which ranged from ∼0.3 to ∼3.8 ks). The upper limits for the non-detections were consistent with the detected luminosities (when fitting a thermal model to the spectrum) of ∼1034 erg s−1 (0.5–10 keV). This level is consistent with what has been measured previously for this source in quiescence. However, on March 17 the source was found to have an order of magnitude larger count rate. When fitting the flare spectrum with an absorbed power-law model, we obtained a flare luminosity of (3–4) × 1034 erg s−1 (0.5–10 keV). Follow-up Swift observations showed that this flare lasted <16 d. This event was very likely due to a brief episode of low-level accretion on to the neutron star and provides further evidence that the quiescent state of neutron-star X-ray transients might not be as quiet as is generally assumed. The detection of this low-level accretion flare raises the question whether the quiescent emission of the source (outside the flare) could also be due to residual accretion, albeit continuous instead of episodic. However, we provide arguments which would suggest that the lowest intensity level might instead represent the cooling of the accretion-heated neutron star.

ESTIMATING THE PROPERTIES OF HARD X-RAY SOLAR FLARES BY CONSTRAINING MODEL PARAMETERS

We compare four different methods of calculating uncertainty estimates in fitting parameterized models to RHESSI X-ray spectra, considering only statistical sources of error. Three of the four methods are based on estimating the scale-size of the minimum in a hypersurface formed by the weighted sum of the squares of the differences between the model fit and the data as a function of the fit parameters, and are implemented as commonly practiced. The fourth method uses Bayesian data analysis and Markov chain Monte Carlo (MCMC) techniques to calculate an uncertainty estimate. Two flare spectra are modeled: one from the GOES X1.3 class flare of 19 January 2005, and the other from the X4.8 flare of 23 July 2002. The four methods give approximately the same uncertainty estimates for the 19 January 2005 spectral fit parameters, but lead to very different uncertainty estimates for the 23 July 2002 spectral fit. This is because each method implements different analyses of the hypersurface, yielding method-dependent results that differ greatly depending on the shape of the hypersurface. For the 23 July 2002 flare data, there is a 95% probability that the low energy cutoff lies below approximately 40 keV, and a 68% probability that it lies in the range 7-36 keV. The low-energy cutoff for the 19 January 2005 flare is more tightly constrained to 107+/-4 keV (68% probability). Using the Bayesian/MCMC approach, we also estimate for the first time probability density functions (PDFs) for the total number of flare accelerated electrons and the energy they carry. For the 23 July 2002 event, these PDFs are asymmetric with long tails orders of magnitude higher than the most probable value, caused by the poorly constrained value of the low-energy cutoff. For the 19 January 2005 flare spectrum, the PDFs for the total number of flare accelerated electrons and their energy are much more symmetric and narrow.

STELLAR CORONAE, SOLAR FLARES: A DETAILED COMPARISON OF σ GEM, HR 1099, AND THE SUN IN HIGH-RESOLUTION X-RAYS

Chandra HETG spectra of the coronally active binary stars sigma Gem and HR 1099 are among the highest fluence observations for such systems taken at high spectral resolution in x-rays with this instrument. We compare their properties to solar flare spectra obtained with the Russian CORONAS-F RESIK instrument at similar resolution in an overlapping bandpass. We emphasize the comparisons of the 3.3-6.1 A region from solar flare spectra to the corresponding sigma Gem and HR 1099 spectra. We also model the the HETG spectra from 1.7-25 A to determine coronal temperatures and elemental abundances. Sigma Gem is a single lined coronally active long period binary which has a very hot corona. HR 1099 is a similar, but shorter period, double lined system. In the deep exposures we study emission from some of the weaker species, such as K, Na, and Al, which have the lowest first ionization potentials (FIP). The solar flare temperatures reach ~20 MK, comparable to the sigma Gem and HR 1099 coronae. During the Chandra exposures, sigma Gem was slowly decaying from a flare and its spectrum is well characterized by a collisional ionization equilibrium plasma with a broad temperature distribution ranging from 2-60 MK, peaking near 25 MK, but with substantial emission from 50 MK plasma. We have detected K XVIII and Na XI emission which allow us to set limits on their abundances. HR 1099 was also in a flare state but had no detectable K XVIII. These measurements provide new comparisons of solar and stellar coronal abundances, especially at the lowest FIP values. The low FIP elements do not show enhancement in the stellar coronae as they do in the Sun, except for K in sigma Gem. Sigma Gem and HR 1099 differ in their emission measure distributions but have very similar elemental abundances.

Reduction in the intensity of solar X-ray emission in the 2- to 15-keV photon energy range and heating of the solar corona

The time profiles of the energy spectra of low-intensity flares and the structure of the thermal background of the soft X-ray component of solar corona emission over the period of January–February, 2003, are investigated using the data of the RHESSI project. A reduction in the intensity of X-ray emission of the solar flares and the corona thermal background in the 2- to 15-keV photon energy range is revealed. The RHESSI data are compared with the data from the Interball-Geotail project. A new mechanism of solar corona heating is proposed on the basis of the results obtained.

Silicon Abundance from RESIK Solar Flare Observations

The RESIK instrument on the CORONAS-F spacecraft obtained solar flare and active-region X-ray spectra in four channels covering the wavelength range 3.8 – 6.1 Å in its operational period between 2001 and 2003. Several highly ionized silicon lines were observed within the range of the long-wavelength channel (5.00 – 6.05 Å). The fluxes of the Si xiv Ly-β line (5.217 Å) and the Si xiii 1s 2 – 1s3p line (5.688 Å) during 21 flares with optimized pulse-height analyzer settings on RESIK have been analyzed to obtain the silicon abundance relative to hydrogen in flare plasmas. As in previous work, the emitting plasma for each spectrum is assumed to be characterized by a single temperature and emission measure given by the ratio of emission in the two channels of GOES. The silicon abundance is determined to be A(Si)=7.93±.21 (Si xiv) and 7.89±.13 (Si xiii) on a logarithmic scale with H=12. These values, which vary by only very small amounts from flare to flare and times within flares, are 2.6±1.3 and 2.4±0.7 times the photospheric abundance, and are about a factor of three higher than RESIK measurements during a period of very low activity. There is a suggestion that the Si/S abundance ratio increases from active regions to flares.

Anomalous resistivity in beam-return currents and hard-X ray spectra of solar flares

Context. Observations of hard-X ray (HXR) spectra from solar flares show that there is noncollisional energy loss when energetic beam electrons are transported along the flare loop from their acceleration site above the looptop in the corona to the loop footpoints in the chromosphere.

JITTER RADIATION MODEL OF THE CRAB GAMMA-RAY FLARES

The gamma ray flares of the Crab nebula detected by Fermi and AGILE satellites challenge our understanding of physics of pulsars and their nebulae. The central problem is that the peak energy of the flares exceeds the maximum energy E_{\mathrm{c}} determined by synchrotron radiation loss. However, when there exist turbulent magnetic fields with scales \lambda_{\mathrm{B}} smaller than 2\pi mc^2/eB, jitter radiation can emit photons with energy higher than E_{\mathrm{c}}. The scale required for the Crab flares is about two orders of magnitude less than the wavelength of the striped wind. We discuss the model in which the flares are triggered by plunging of the high density blobs into the termination shock. The observed hard spectral shape may be explained by jitter mechanism. We make three observational predictions: firstly the polarization degree will become lower in flares, secondly, no counterpart will be seen in TeV-PeV range, and thirdly the flare spectrum will not be harder than \nu F_\nu \propto \nu^1.

The emission in the region [formula omitted] during disk and limb faint solar flares

Hard X-ray and gamma-ray emission in energy band E>50keV was first observed by AVS-F apparatus onboard CORONAS-F satellite (detector SONG-D) during some solar flares with classes B and C by GOES classification. Such component registered in flares with duration less than 30min. However γ-emission up to several tens of MeV was observed during some classes B and C events, which temporal profiles were not corresponded to Neupert effect. For example, during class B2.3 limb solar flare January 7, 2005 maximum observed energy was Emax∼36MeV and during class B4.6 disk solar event January 12, 2005 maximum observed energy was Emax∼7MeV. Properties of temporal profiles and energy spectra of faint solar flares, during which emission in the energy band of E>0.1MeV were registered are discussed in the presented work. There is not any strong correlation between presence or absence of hard X-ray and γ-ray emission and the intensity of soft X-ray emission during solar flares. The one of illustration of this fact is the absence of any observed statistically significant count rate exceed above background level during some class M flares in the energy band E>0.1MeV. The typical example of such flares is event November 8, 2001 (class M4.2, lasts from 14:59 UT up to 16:00 UT, maximum of soft X-ray emission was at 15:35 UT on GOES data).

Solar flares as proxy for the young Sun: satellite observed thermosphere response to an X17.2 flare of Earth's upper atmosphere

Abstract. We analyzed the measured thermospheric response of an extreme solar X17.2 flare that irradiated the Earth's upper atmosphere during the so-called Halloween events in late October/early November 2003. We suggest that such events can serve as proxies for the intense electromagnetic and corpuscular radiation environment of the Sun or other stars during their early phases of evolution. We applied and compared empirical thermosphere models with satellite drag measurements from the GRACE satellites and found that the Jacchia-Bowman 2008 model can reproduce the drag measurements very well during undisturbed solar conditions but gets worse during extreme solar events. By analyzing the peak of the X17.2 flare spectra and comparing it with spectra of young solar proxies, our results indicate that the peak flare radiation flux corresponds to a hypothetical Sun-like star or the Sun at the age of approximately 2.3 Gyr. This implies that the peak extreme ultraviolet (EUV) radiation is enhanced by a factor of about 2.5 times compared to today's Sun. On the assumption that the Sun emitted an EUV flux of that magnitude and by modifying the activity indices in the Jacchia-Bowman 2008 model, we obtain an average exobase temperature of 1950 K, which corresponds with previous theoretical studies related to thermospheric heating and expansion caused by the solar EUV flux.

Nuclear γ-ray line emission induced by energetic ions in solar flares and by galactic cosmic rays

The γ-ray spectra ol the strongest solar flares often show a broad and complex structure in the 0.1-10 MeV region sitting on a bremsstrahlung continuum. This structure is composed of several outstanding narrow lines and of thousands of unresolved narrow and broad lines forming a quasi-continuum. The major part of this emission is due to prompt deexcitation lines following nuclear interactions of accelerated light and heavy ions with the atomic nuclei composing the solar atmosphere. A similar emission is expected from interactions of galactic cosmic rays with the interstellar gas and dust. Experimental nuclear reaction studies coupled with extensive calculations have been done in the last one and a half decade at Orsay for the modelisation of this γ-ray emission. After a description of the nuclear reaction studies the analysis of one solar flare spectrum and predictions for the emission from the inner Galaxy will be presented.

SOLAR ENERGETIC PARTICLE EVENTS AND THE KIPLINGER EFFECT

The Kiplinger effect is an observed association of solar energetic (E > 10 MeV) particle (SEP) events with a soft-hard-harder (SHH) spectral evolution during the extended phases of the associated solar hard (E > 30 keV) X-ray (HXR) flares. Besides its possible use as a space weather predictor of SEP events, the Kiplinger effect has been interpreted as evidence of SEP production in the flare site itself, contradicting the widely accepted view that particles of large SEP events are predominately or entirely accelerated in shocks driven by coronal mass ejections (CMEs). We review earlier work to develop flare soft X-ray (SXR) and HXR spectra as SEP event forecast tools and then examine recent Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) evidence supporting the association of SHH HXR flares with large SEP events. We point out that ad hoc prediction criteria using the CME widths and SXR flare durations of associated RHESSI hard X-ray bursts (HXBs) can yield results comparable to those of the SHH prediction criteria. An examination of the RHESSI dynamic plots reveals several ambiguities in the determination of whether and when the SHH criteria are fulfilled, which must be quantified and applied consistently before an SHH-based predictive tool can be made. A comparative HXR spectral study beginning with the large population of relatively smaller SEP events has yet to be done, and we argue that those events will not be so well predicted by the SHH criteria. SHH HXR flares and CMEs are both components of large eruptive flare events, which accounts for the good connection of the SHH HXR flares with SEP events.