Solar-terrestrial Disturbances Research Articles

September 2017 Solar Flares Effect on the Middle Atmosphere

This paper examines the response of the upper atmosphere to increased radiation following exceptional solar activity in September 2017. The active region of the Sun AR2673 has caused intense solar-terrestrial disturbance. This active region has generated several powerful X-class solar flares. The strongest outburst of the 24th solar activity cycle X9.3 occurred on 6 September 2017. The second powerful solar flare X8.2 occurred on 10 September 2017. Both flares caused an increase of the solar irradiance in extreme ultraviolet and soft X-ray spectral regions, and Ly-α line. The empirical FISM2 model was used to obtain data on the radiation fluxes from solar flares. The HAMMONIA chemistry–climate model was used to analyze the effect of radiation on the neutral atmosphere. This work presents the results of the effect of solar flares on the chemical composition and ozone of the upper and middle atmosphere.

Installation and preliminary data analysis of Penang magnetic data Acquisition system (MAGDAS) in Malaysia

MAGDAS PEN was established on 19th September 2019 as one of the MAGDAS observatory arrays located at Universiti Sains Malaysia (USM) (5.15°, 100.50°). The main objective of the MAGDAS project is to monitor global electromagnetic and the ambient plasma density in the geospace environment. This installation has contributed to a better understanding of the Sun-Earth coupling system. This paper presents the installation process of one of the MAGDAS magnetometers named YU-8 T magnetic sensor and provides a preliminary analysis of geomagnetic HDZ components amplitude-time that was observed at PEN station. A one-month HDZ-geomagnetic field data was processed from 1st November to 30th November 2019. The daily variations with a consistent pattern in delta H geomagnetic field components are observed throughout the day with eastward electric field effects that are observed during solar peak hours. The delta H-component gradually increases around 0700LT and reaches the maximum reading at 1300LT with a range of value ~ 40-70nT. The value slowly decreases that started from 1400LT until the night time. The reading during the night time shows a constant variation with magnitude varies in between −10nT to + 10nT. The average H-component value of the night time is used as the baseline for the observation system. Overall, the observed trends portray a good sign of solar quiet field and Sq with no solar-terrestrial disturbances.

Investigation of exceptional solar activity in September 2017: GLE 72 and unusual Forbush decrease in GCR

The exceptional solar activity in early September 2017 at minimum of solar cycle 24 is analyzed. Intensive solar-terrestrial disturbances was caused by Active Region AR2673, which produced four powerful eruptions class X, including the strongest flare X9.3 of Solar Cycle 24 on September 6, 2017, after which began G4 – Severe geomagnetic storm on 07-08.09.2017 with Ap = 96, and also the second strongest flare X8.2 of Solar Cycle 24 on September 10, 2017, which generated Ground Level Enhancement (GLE) of cosmic rays. This was GLE72 with increase of solar cosmic ray flux 6% in Oulu Station (Finland) (effective vertical geomagnetic cutoff rigidity: 0.8 GV), and increase 9% in DOMC Antartica and 14% in DOMB Antartica (in the latter case - lead free neutron monitors with effective vertical cutoff rigidity <0.01 GV). The GLE72 develops under the conditions of a deep Forbush decrease (around 15%) in South Pole cusp caused by September 7th Coronal Mass Ejection. The Forbush effect ends on September 11th (http://cosmicrays.oulu.fi). But cosmic ray measurements by flying balloons to the stratosphere over California show that after solar eruptions in September 2017 the radiation levels in stratosphere took more than two months to fully rebound to the conditions of minimal solar activity. This is interesting fact which deserves to be explored in detail. It is precisely the study and interpretation of this process that is concerned with this work.

Re-visit of ionosphere storm morphology with TEC data in the current solar cycle

This paper addresses the magnetosphere–ionosphere–thermosphere (M–I–T) storm effects, with emphasis on 15 major geomagnetic storms in the current solar cycle as far as May 2015. It is an ionosphere storm response-case analysis based on the vertical total electron content (VTEC) observations at mid-latitude Global Positioning System (GPS) ground-based station HERS (0.33°E, 50.86°N). The time dependent features of ionospheric storms are examined with ∆VTEC defined as the percent change of VTEC during storm time relative to quiet time represented by its monthly median value at the same UT. During a specific event of April 2010 storm, the F2 layer peak electron density (NmF2) data at collocated Chilton (358.67°E, 51.70°N) ionosonde station are used for comparison. The seasonal dependence of the storms is identified and the strength of both positive and negative storms phases is correlated with the intensity of the geomagnetic storms. The focus is on localized characteristics of these solar–terrestrial disturbances and the relative roles of inherent physical and chemical processes that appear to be so changeable from one event to the other generating significant variability in ionospheric responses. The implications of these results for the persistence, certainty and consequently predictability of ionosphric storms are discussed and conclusions drown.

MHD nature of the origination, dynamics, geoeffectiveness, and disappearance of the four-sector structure of the solar magnetic field during the cycle 23 decline phase

The MHD nature of the origination, dynamics, geoeffectiveness, and disappearance of the four-sector structure of the solar magnetic field during the cycle 23 decline phase has been established. A prolonged ordered MHD process including the chain of the interrelated phenomena (unknown before this study), which begin and end in one of the main zones of active longitudes and are responsible for the above nature of the four-sector structure, has been detected as a result of the simulation of the large-scale open solar magnetic field and an analysis of the dynamics of this field fluxes. These phenomena are as follows: the extreme concentration of the photospheric field sources of the same sign in the zone of active longitudes; blocking of regular differential rotation by these sources; origination of a nonstationary MHD disturbance in the form of a four-sector structure, traveling in the direction of solar rotation at a nearly Alfven velocity; upset of blocking, displacement of blocking sources from the zone, and their shearing motion relative to a traveling MHD disturbance; deceleration and dissipation of a four-sector MHD disturbance; and reconstruction of a bisector structure. The interactions during this process, which lasted from May 2004 to December 2005, were accompanied by the generation of an ordered succession of heliospheric and solar-terrestrial disturbances including the series of nine extrastorms that were observed from July 2004 to September 2005 and were the last storms in the finished cycle 23 of solar activity.

Correct normalization of the &lt;i&gt;Dst&lt;/i&gt; index

The Dst index has been one of the most important solar-terrestrial indices for decades, and it is used in numer- ous studies as a measure of the temporal development and intensity of magnetic storms and the ring current. Here we discuss two issues related to the relative and absolute normal- ization that are problematic to the Dst index. We show for the first time quantitatively that the magnetic disturbances at the four Dst stations are ordered according to the latitudinal pro- jection of an equatorial disturbance upon the local horizontal of the geomagnetic field. Therefore, the distur- bances observed at each station should be first normalized by the cosine of the geomagnetic latitude of the station before they are averaged to form the Dst index. Perhaps surpris- ingly, the recipe to calculate the Dst index does not include this normalization and, therefore, must be revised on this part. We also discuss the effects of correcting the quiet-time seasonal variation, the so called non-storm component in the Dst index. This correction is seasonally varying, being largest around equinoxes and smallest at solstices, leading to an average correction (increase) of about 6 nT, i.e. about 25-30%, for annual averages of the Dst index. This increase also leads to significantly improved correlations between the corrected Dst index, the so called Dcx index, and many other indices of solar-terrestrial disturbance. We show here in de- tail that the correlation between the geomagnetic Ap index and the Dcx index (cc = 0.83) is much higher than between Ap and Dst (cc = 0.60). These results give further evidence that the Dcx index is a more truthful measure of magnetic storminess than the original Dst index.

The applicability of model based aircraft radiation dose estimates

The monthly cosmic radiation modulation parameters provided to compute radiation dose on aircraft flights do not account for short-term temporal variations such as Forbush decreases or high-speed solar wind flows. The currently available radiation dose models also do not account for changes in geomagnetic conditions when the geomagnetic cutoff may be significantly lower than the average predicted by use of the international geomagnetic reference field models. We utilize on-board aircraft radiation dosimeter data acquired during the major solar-terrestrial disturbances of October/November 2003 to demonstrate these effects along with the increased dose due to the ground-level event of 29 October 2003 on a mid-latitude flight path.

The 1859 Solar–Terrestrial Disturbance And the Current Limits of Extreme Space Weather Activity

It is generally appreciated that the September 1859 solar–terrestrial disturbance, the first recognized space weather event, was exceptionally large. How large and how exceptional? To answer these questions, we compiled rank order lists of the various measures of solar-induced disturbance for events from 1859 to the present. The parameters considered included: magnetic crochet amplitude, solar energetic proton fluence (McCracken et al., 2001a), Sun–Earth disturbance transit time, geomagnetic storm intensity, and low-latitude auroral extent. While the 1859 event has close rivals or superiors in each of the above categories of space weather activity, it is the only documented event of the last ∼150 years that appears at or near the top of all of the lists. Taken together, the top-ranking events in each of the disturbance categories comprise a set of benchmarks for extreme space weather activity.

Australian magnetic field effects during geomagnetic storms

Using Australian records, we studied six isolated geomagnetic storms for the regional effects of their associated magnetic fields, emphasizing the linear regression correlation coefficient between station locations and indices. An innovation used here was to consider both the full magnetic disturbance field and a form of this field with the smoothed storm-time Dst values removed to feature the small variations. Magnetic H-component data from paired stations throughout the continent showed correlation values of +0.90 to +0.97. These results indicate the adequacy of the present density of observatories in Australia and their value for use with aeromagnetic surveys. The planetary magnetic ap index was found to have an inconsistent relationship to Australian H-component fields. The planetary magnetic Dst index was successfully represented by data from four Australian observatories. The discovered capability of Australian magnetic observatories to represent the magnetic storm Dst index in real time, combined with the established lognormal-form characteristic of Dst, means that Australian solar-terrestrial disturbance centers should be able to predict the time to recovery of quieter fields once an on-line Austrialian magnetic field Dst mainphase computation has been made.

Solar Eruptions - the Effects on the Earth’s Environment

AbstractThe response of our space environment to the constantly changing Sun is known as ”Space Weather”. The Solar and Heliospheric Observatory (SOHO) has obtained significant new information about coronal mass ejections (CMEs), the source of the most severe disturbances in the Earth’s environment. Most of the time space weather is of little concern in our everyday lives. However, when the space environment is disturbed by the variable outputs of the Sun, technologies that we depend on both in orbit and on the ground can be affected. The increasing deployment of radiation-, current-, and field-sensitive technological systems over the last few decades and the increasing presence of complex systems in space combine to make society more vulnerable to solar-terrestrial disturbances. Thus, our society is much more sensitive to space weather activity today compared to the last solar maximum. By observing the Sun 24 hours per day, SOHO has proved to be an important “space weather watchdog”. The importance of real-time monitoring of the Sun will be pointed out and a number of enterprises affected by space weather will be discussed.

New evidence for the quasi-steady structure, phase reversal and drift in the solar-terrestrial corotating disturbances

The quasi-steady structures in the corotating solar-terrestrial disturbances and their phase reversal reappear in the solar cycle 21 and 22, which confirms that the above phenomenon found by the authors is a regular feature occurring on a time scale of one century. Moreover, the geomagnetic disturbance data covering the past one hundred years up to 1991–1992 indicated that the quasi-steady corotating structure in the even cycles tends to drift linearly in peak against solar rotation. A tentative prediction is made for the corotating disturbances which may appear in the forthcoming pre-minimum years.

Recent progress in satellite radio beacon studies with particular emphasis on the ATS-6 radio beacon experiment

In May 1974 a new era in satellite radio beacon studies of the ionosphere opened with the ATS-6 Radio Beacon Experiment. The history of radio beacon studies up to that time is reviewed briefly and the particular features of the ATS-6 beacon are discussed together with the basic theory required to interpret the measurements. The main emphasis is on the ATS-6 beacon experiment but other beacon data are discussed which provide the necessary background. The diurnal and seasonal variations of the total electron content and the plasmaspheric content are presented for the U.S.A. and Europe. In winter the plasmaspheric content over the Western Hemisphere maximizes at night while in Europe and the Pacific it appears to peak near noon. This is thought to be caused by flow of plasma from the local and conjugate ionospheres. Night maxima of total electron content are found showing that they do not arise from depletions of the plasmaspheric content. The plasmaspheric content is highly sensitive to solarterrestrial disturbance, it reaches a minimum on the third day of a storm and may take between 10 and 20 days of partial filling and emptying to recover. Traveling disturbances in U.S.A., Europe, and India show similarities of speeds but not of direction. Beacon observations of micropulsations in total content, tropospheric fluctuations and Fresnel diffraction by intense ionospheric irregularities are discussed together with radio wave scintillations and some applications of beacon radio data to communications and navigation.

Ionization enhancement in the middle latitude D-region due to precipitating high energy electrons

For several days following a large solar-terrestrial disturbance in August 1972 increases in energetic electron flux at 1400 km, L = 2.6 were observed by instruments on the satellite ISIS-2 and unusually high daytime electron densities were observed in the lower D-region above Christchurch, New Zealand (also at L = 2.6). These observations, together with calculations of ionization production rates in the D-region based on the observed pitch angle distribution at the satellite are direct evidence for the importance of precipitating energetic electrons as an ionization source in the lower D-region at middle latitudes following magnetic storms.

オメガ信号の擾乱 : ことに高緯度帯の航行中における

OMEGA propagation disturbances have been studied by the author and he presented the two papers already, but the experimental results were reanalised by the solar terrestrial physical and geomagnetic data published later. Examining the results of twice trans-Pacific experiments made in 1969 and 1971, it was ascertainable that more significant features of OMEGA disturbances were found at high latitudes, and the phase fluctuations of sudden change were great and rapid. In this paper, however, the author publishes Magnetic anomalies and Aurora hiss. The magnetic storm occured along the propagation path of OMEGA signal gives rise to the propagation disturbances. The phenomena discussed here were shown in the following predominant pattern. Namely, fluctuation of OMEGA signal synchronized completely with the geomagnetic anomalies. In the precise description, when the magnetic variarion set in maximum, the phase disturbance was started, the phenomena during the anomalies were lasted, and it ceased when the variation recovered the original value. The duration was about 9 hours and the fluctuation was 20 cel in maximum. Additionally, aurora hiss was observed frequently around the Aleutian Islands. Through the experiments, the author would propose that simple field strength meter of signal was an useful detector for the solar terrestrial disturbances capable of avoiding the systematic error.

A Lunar-Month Modulation of Large Solar-Terrestrial Disturbances

Dodson and Hedeman discovered an unexpected effect in the occurrence of solar proton events as revealed by polarcap absorption (PCA). When the 48 events in Bailey’s Catalog of the Principal PCA Events, 1952-1963 are distributed with the phase of the moon there is a gap of several days near full moon; also, many more events occur when the moon waxes than when it wanes. Dodson and Hedeman did not find similar, apparent departures from random distribution either with a mean solar rotation period of 27.3 days or for solar flare events. They concluded that ‘at the present time it is not clear whether the 29.5 day “effect” is related to the sun or the moon or is only a statistical accident’.

Mariner II: High-Energy-Radiation Experiment

The radiation experiment on Mariner II was undertaken to investigate the dependence of the intensity of ionizing radiation in space upon distance from the sun; temporal variations of the radiation and their correlation with measurements of the magnetic field and plasma flux at the location of the spacecraft, and with solar-terrestrial disturbances; and the irtensity and extert of magnetically trapped radiation, if any, around Venus. Results are briefly discussed.

Natural electromagnetic field fluctuations in the 3.0- to 0.02-cps range

Using large loop antennas the ultra-low-frequency research group at the National Bureau of Standards has studied the upper atmosphere phenomena of geomagnetic micropulsations. Data taken at a number of world stations on both direct reading chart and magnetic tape indicate a division into three contributing phenomena for the frequency range of 3.0 to 0.02 cps. Very regular oscillations of 2.0 to 0.2 cps are a strange pulsation phenomenon most likely of outer atmospheric origin but apparently unrelated to solar-terrestrial disturbances. Sudden bursts of large amplitude field fluctuations spread throughout the frequency range are closely related to high latitude particle precipitation, enhanced ionospheric absorption, and auroral luminosity; these fluctuations seem to be of ionospheric origin. Regular oscillations between 0.2 and 0.03 cps appearing over broad sections of the earth with related phase on days of high solar-terrestrial activity are presently the best candidate for magneto-hydrodynamic interpretation. During the International Quiet Sun Year (IQSY) a configuration of world stations will be operated along a latitudinal line covering about 180° at three sites in the boreal auroral zone, along a longitudinal line near 75° to 80°W longitude with conjugate stations corresponding to L shell values of about 6.5 and 4, and at an equatorial site.

Solar Radio Bursts and Low-energy Cosmic-rays

THE recent discovery, by equipment carried in satellites and balloons, that the terrestrial atmosphere is frequently bombarded by solar protons of energies 30–300 MeV.1,2, has given rise to much speculation concerning the origin of these low-energy cosmic rays, and their relation to solar radio bursts, flares, and terrestrial disturbances. In this communication we seek to elucidate these problems from a consideration of radio spectral observations of the Sun. The radio data were obtained at the Harvard Radio Astronomy Station, Fort Davis, Texas, with sweep-frequency receivers3 covering the range 25–580 Mc./s. The equipment scans the entire frequency-range three times per second, and a continuous record of solar radio bursts has been obtained from sunrise to sunset for the past three years.

Notes on the Time Relation between Solar Emission and Terrestrial Disturbances

Although the correlation between general solar activity and terrestrial disturbances is quite evident, the association of individual storms with specific sunspot groups has never been very satisfactory. Disturbances sometimes have occurred when no sunspots were visible and at other times large sunspots have been unaccompanied by any abnormal disturbances. A possible explanation of such anomalies may lie in longer transit times for the disturbing solar emission than is usually assumed. Some indication is given in this paper that these transit times may range from periods as short as only one or two days to as much as three months. The corresponding velocities for the above transit times are of the order of 2000 and 20 kilometers per second. Curves show the approximate relation between the angle of emission, velocity, day of emission, and the days intervening between the passage of a spot through the central meridian of the sun and the corpuscular encounter with the earth.