Recovery Phase Of Magnetic Storm Research Articles

Variability of ionospheric ionization over Eurasia according to data from a high-latitude ionosonde chain during extreme magnetic storms in 2015

. We have examined longitudinal-temporal variations in ionospheric parameters over Eurasia by analyzing data from a chain of high-latitude ionosondes along a latitude circle ~70° N (geomagnetic latitudes 58°<Glat<65°) in the longitudinal sector 26–171° E during severe magnetic storms of solar cycle 24 in March and June 2015. To analyze the response of ionospheric ionization to geomagnetic disturbances, we have used ionosonde data on hourly average critical frequency foF2 of the ionospheric F2 layer. Strong differences were observed between common peculiarities of temporal variations in foF2 for the analyzed periods of magnetic storms, which are likely associated with the characteristic features of the seasonal and diurnal variations in the background high-latitude ionosphere of the given geographic region. During the main and early recovery phases of magnetic storms there were periods of blackouts of ionosonde radio signals. Differences in the character of the ionospheric response to geomagnetic disturbances have been noted. This is probably due to seasonal features of the probability of occurrence of the ionospheric storm positive or negative phase in different seasons of the year. The trends of increasing ionospheric ionization over the vast region of Eastern, Western Siberia and Europe after the end of the extreme magnetic storm in March 2015, according to measurements from the chain of high-latitude ionosondes, may be associated with the formation of an area of increased [O]/[N₂] ratio over this territory. Such an increase in ionospheric ionization exceeding the background level of foF2 values can be considered as a clear manifestation of the after-effect of magnetic storms.

Изменчивость ионизации ионосферы над Евразией по данным цепи высокоширотных ионозондов во время экстремальных магнитных бурь 2015 г.

. We have examined longitudinal-temporal variations in ionospheric parameters over Eurasia by analyzing data from a chain of high-latitude ionosondes along a latitude circle ~70° N (geomagnetic latitudes 58°<Glat<65°) in the longitudinal sector 26–171° E during severe magnetic storms of solar cycle 24 in March and June 2015. To analyze the response of ionospheric ionization to geomagnetic disturbances, we have used ionosonde data on hourly average critical frequency foF2 of the ionospheric F2 layer. Strong differences were observed between common peculiarities of temporal variations in foF2 for the analyzed periods of magnetic storms, which are likely associated with the characteristic features of the seasonal and diurnal variations in the background high-latitude ionosphere of the given geographic region. During the main and early recovery phases of magnetic storms there were periods of blackouts of ionosonde radio signals. Differences in the character of the ionospheric response to geomagnetic disturbances have been noted. This is probably due to seasonal features of the probability of occurrence of the ionospheric storm positive or negative phase in different seasons of the year. The trends of increasing ionospheric ionization over the vast region of Eastern, Western Siberia and Europe after the end of the extreme magnetic storm in March 2015, according to measurements from the chain of high-latitude ionosondes, may be associated with the formation of an area of increased [O]/[N₂] ratio over this territory. Such an increase in ionospheric ionization exceeding the background level of foF2 values can be considered as a clear manifestation of the after-effect of magnetic storms.

Evaluation of the Dix Scaling Factor During Geomagnetically Disturbed Periods Over South America

In this work, we present a study of the Total Electronic Content (TEC) spatiotemporal variability during geomagnetically disturbed periods over South America. For this, we evaluated the Disturbance Ionosphere indeX (DIX) scaling factor (β coefficient) for different magnetic dip angles and seasons. In this context, the β values are given in TEC units (TECU) and correspond to a latitudinal-dependent factor used to normalize the DIX output into a scale from 0 to 5. Thus, we selected thirteen magnetic storm events between 2013 and 2017, subdivided into seven moderate, four intense, and two extreme magnetic storms. The results showed that the β coefficient latitudinal variation is characterized by two asymmetric crests concerning the magnetic equator. This suggests the presence of transequatorial thermospheric wind's effects on the ionosphere's plasma distribution. Additionally, we have observed that the crests occur close to the magnetic equator during the winter and autumn and at higher latitudes during summer and spring. Additionally, we have noticed a drastic decrease in the daily highest β-values before the Storm Sudden Commencement (SSC) stage of the studied events and during the magnetic storm recovery phase. This behavior highlights the expected scenario of quiet conditions with no TEC disturbance.

Simulation of ionospheric parameters for September 2017

Modeling the parameters of the ionosphere is an important part of the process of studying the influence of space weather factors. This paper is devoted to modeling three parameters of the ionosphere (critical frequency foF2, total electron content TEC, and equivalent slab thickness τ) related to the possibility of determining foF2 on a global scale using TEC. Comparison of the model τ(IRI), τ(IRI-Plas) adapted to the observational TEC, τ(NSTM) with the observational median τ(med) for four ionosondes along the 30° E meridian in September 2017 showed the best fit for the IRI-Plas model. Using a polynomial approximation of τ(med) and the distribution of TEC along this meridian in the range of 30° N-70° N, the features of the response of TEC and foF2 to disturbances in September 2017 were revealed. The results for September 7-8, which showed positive enhancements of TEC and foF2, coincide with the results of other researchers. The similarity of this response with the response to the disturbance on September 27-28, which is not associated with a solar flare, is revealed. It is shown that the unique enhancement on September 11 during the magnetic storm recovery phase, identified in the Asian-Australian sector (Lei et al., 2018), is not observed at the 30° E meridian. The global longitudinal distributions of TEC at latitudes of 50° and 30° showed the locality of this phenomenon.

The Accuracy Assessment and Scientific Research Progress of Ionospheric Radio Occultation Products Observed by Fengyun-3 GNOS

Global Navigation Satellite System (GNSS) Radio Occultation (RO) is a novel detection technique that can provide global ionospheric products with high vertical resolution, high precision, and low cost. In recent years, China has launched the FY3 series of meteorological satellites carrying the first RO payload to simultaneously receive GPS (Global Positioning System) and BDS (BeiDou Navigation System) signals. In the accuracy assessment of RO products observed by GNOS (GNSS Occultation Sounder), the maximum F2-layer electron density (NmF2) of GPS occultation and BDS occultation have a standard deviation (std) of less than 20% in comparison with that of ionosondes. The std of F-layer worst-case ionospheric scintillation index ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$S4_{max}^F$</tex-math></inline-formula> ) between COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) and FY3/GNOS is less than 0.1. The above results prove the high precision of FY3 ionospheric RO products. The RO products have been applied to preliminary scientific research and applications, e.g., the process of main phase and recovery phase of magnetic storms revealed by the NmF2 observed by FY3C/GNOS, the pre-midnight dynamics of F-layer strong scintillation during magnetic storms revealed by GNOS scintillation data, the ionospheric perturbation driven by Tonga volcano eruption revealed by FY3/GNOS, applications of the RO data for the research of sporadic E layers, evaluation of IRI model in statistics and ionospheric climatological characteristics, etc. With the successive network observation and continuous deployment of FY3 meteorological satellites, the continuous improvement of GNOS payload and the BDS system, massive high-precision ionospheric RO products will be developed and show more significant value.

High-Latitude Geomagnetic Disturbances and Field Aligned Currents in the Recovery Phase of the Large Magnetic Storm on June 21–26, 2015

High-Latitude Geomagnetic Disturbances and Field Aligned Currents in the Recovery Phase of the Large Magnetic Storm on June 21–26, 2015

Multi‐Event Analysis of Plasma and Field Variations in Source of Stable Auroral Red (SAR) Arcs in Inner Magnetosphere During Non‐Storm‐Time Substorms

AbstractStable auroral red (SAR) arcs are optical events with dominant 630.0‐nm emission caused by low‐energy electron heat flux into the topside ionosphere from the inner magnetosphere. SAR arcs are observed at subauroral latitudes and often occur during the recovery phase of magnetic storms and substorms. Past studies concluded that these low‐energy electrons were generated in the spatial overlap region between the outer plasmasphere and ring‐current ions and suggested that Coulomb collisions between plasmaspheric electrons and ring‐current ions are more feasible for the SAR‐arc generation mechanism rather than Landau damping by electromagnetic ion cyclotron waves or kinetic Alfvén waves. This work studies three separate SAR‐arc events with conjunctions, using all‐sky imagers and inner magnetospheric satellites (Arase and Radiation Belt Storm Probes [RBSP]) during non‐storm‐time substorms on December 19, 2012 (event 1), January 17, 2015 (event 2), and November 4, 2019 (event 3). We evaluated for the first time the heat flux via Coulomb collision using full‐energy‐range ion data obtained by the satellites. The electron heat fluxes due to Coulomb collisions reached ∼109 eV/cm2/s for events 1 and 2, indicating that Coulomb collisions could have caused the SAR arcs. RBSP‐A also observed local enhancements of 7–20‐mHz electromagnetic wave power above the SAR arc in event 2. The heat flux for the freshly detached SAR arc in event 3 reached ∼108 eV/cm2/s, which is insufficient to have caused the SAR arc. In event 3, local flux enhancement of electrons (&lt;200 eV) and various electromagnetic waves were observed, these are likely to have caused the freshly detached SAR arc.

A Possible Mechanism on the Detachment Between a Subauroral Proton Arc and the Auroral Oval

AbstractSubauroral proton arcs are a type of terrestrial auroral phenomena, which are often detached equatorially from the auroral oval. This work presents evolution of a subauroral proton arc using observations of the Special Sensor Ultraviolet Spectrographic Imager and Special Sensor J (SSJ) on board Defense Meteorological Satellite Program (DMSP) spacecraft. The arc was observed in the afternoon sector and was located within 60°–70° geomagnetic latitude during the recovery phase of a moderate magnetic storm with the minimum SYM‐H index of −55 nT. Particle measurements from DMSP F17/SSJ indicate that the arc was detached from the normal oval and produced by energetic ring current ions with energies above 10 keV. These energetic ions were likely scattered into the magnetic loss cone by electromagnetic ion cyclotron waves in the frequency range between 0.1 and 0.5 Hz, as confirmed by Pc1 waves derived from the observations of a ground station. Continuous auroral observations directly show that the subauroral proton arc was detached from the oval during evolution. Following a northward interplanetary magnetic field turning, the auroral oval moved toward higher latitudes. We propose that the equatorward edge of the auroral oval is less influenced by the convection electric field, and thus moves more slowly than the poleward edge. This mechanism is proposed for producing a separation between the equatorward and poleward parts of the auroral oval, with the former evolving into the subauroral proton arc.

Evolution of High-Latitude Geomagnetic Disturbances during the Magnetic Storm of July 22, 2009

The behavior of geomagnetic disturbances during a moderate CIR storm, the most intense magnetic storm of 2009 in the solar activity minimum are considered. It is found that the substorm activity during the main phase of the storm was observed not in the nighttime but in the morning sector (0700–0900 MLT) of auroral geomagnetic latitudes (65°–67°) and was accompanied by extremely large (up to 1000 nT) geomagnetic pulsations of the Рс5 range, evidently of a non-resonant nature; the amplitude of the Y component of waves considerably exceeded that of the Х component. In the recovery phase of the magnetic storm, the tangential discontinuity in the IMF caused a substorm observed near the polar boundary of the auroral oval in the global scale in the longitude, from the evening sector to midday hours. In the daytime sector, the magnetic bay was observed several minutes later than in the nighttime sector and rapidly moved to the pole, which can be interpreted as the motion to the pole of the boundary between closed and open geomagnetic field lines and contraction of the auroral oval.

The Influence of Disturbance Dynamo Electric Field in the Formation of Strong Sporadic E Layers Over Boa Vista, a Low‐Latitude Station in the American Sector

AbstractThis study analyzes strong sporadic E layer (Es) formation in Boa Vista (BV, 2.8°N, 60.7°W, dip: 18°), a low‐latitude region in the Brazilian sector, which occurred far after the onset of a magnetic storm recovery phase. Such occurrences were observed during seven magnetic storms with available data for BV. Thus, the ionospheric behavior on days around the magnetic storm that occurred on 20 January 2016 was investigated to search for possible explanations. This analysis indicated that the probable mechanism acting during the Es layer strengthening is the zonal westward electric field caused by a disturbance dynamo. The same evidence was also observed in two other magnetic storms at the same location. Hence, a numerical model of the E region dynamics, called MIRE (Portuguese acronym for E Region Ionospheric Model), was used to confirm whether the disturbance dynamo could cause the Es layer intensification. The inputs for the model were the electric field deduced from the vertical drift and the wind components provided by GSWM‐00 model. The simulations indicate that the Es layer density is significantly enhanced when the zonal electric field is present compared to the reference scenario with only the winds. Therefore, it is concluded that the disturbance dynamo electric field is the likely cause of the strong Es layers in the analyzed cases. Finally, the combined results from the model and observational data seem to contribute significantly to advance our understanding of the role of the electric fields in the Es layer formation at low latitudes.

Daytime VLF Emissions during the Magnetic Storm Recovery Phase: the Event of January 5, 2015

This paper discusses the spectral and temporal features of the 7-h daytime VLF noise emission burst in the frequency band of 1‒10 kHz observed on the Earth’s surface during the late recovery phase of a moderate magnetic storm (Kр = 5 and Dst ~ –80 nT) under nearly quiet space weather. These VLF emissions were recorded simultaneously at two auroral stations located at a geomagnetic latitude of ~64° MLAT and at a longitude distance of ~400 km from each other: Finnish Kannuslehto Station (KAN) and Russian Lovozero Observatory (LOZ). The dynamic VLF wave spectrum is considered at different time scales. During the development of the discussed daytime VLF burst, the noise emissions at below 3.5 kHz gradually turn into periodic (QP) emissions with a quasi-repetition of ~3 s. Having compared the directions of short isolated high-frequency (above 5 kHz) VLF signals (so-called “birds”) arriving at KAN and LOZ, we draw conclusions on the possible location and spatial dynamics of the exit area of emission from the ionosphere.

Observations of ULF Waves at the Late Recovery Phase of Magnetic Storm

利用Radiation Belt Storm Probes（RBSP）和Magnetospheric Multiscale（MMS）的联合观测研究了2016年1月25日和2月22日的两个超低频（ULF）波动事件.这两个事件均发生在磁暴的恢复相后期，波动分布在晨侧与正午之间的区域.RBSP观测到的两次波动都发生在低<i>L</i>-shell（4.7～5.8），MMS观测到的两次波动都发生在高<i>L</i>-shell（8.0～14.2）.在高<i>L</i>-shell，超低频波偏振以环向波为主，沿磁力线方向为基频谐波.在低<i>L</i>-shell，超低频波偏振以径向波为主，沿磁力线方向为二次谐波.对内磁层（<i>L</i><6）中的ULF波，通过比较<i>&#8706;f</i>/<i>&#8706;w</i>|<i>μ,L</i>和（d<i>L</i>）/（d<i>W</i>）（<i>&#8706;f</i>）/（<i>&#8706;L</i>）|<i>μ,W</i>的绝对值可知，bump-on-tail的离子分布和向地的离子相空间密度梯度通过<i>N</i>=1的弹跳共振，共同为波动的产生提供自由能.多重事例分析表明，在磁暴恢复相后期，约10keV的离子伴随着波动的存在而存在，并且为波动的产生提供自由能.

Isolated Auroral Spots Observed by DMSP/SSUSI

AbstractThis work reports auroral spots event observed by the SSUSI instruments on board the DMSP spacecraft between 22 and 23 July 2009 during the recovery phase of a moderate magnetic storm. The spots were observed between 18:00 and 02:00 magnetic local time and stayed at ~60° magnetic latitude. They lasted for ~10 hr and corotated with ~64% of the Earth's rotational speed. In situ observations indicate that the isolated auroral spots were produced by energetic ions at energies between 10 and 240 keV, with significantly anisotropic electron (30–300 keV) precipitations. It is expected that the energetic ions originate from the ring current and can be scattered by the EMIC waves through cyclotron resonance. The energetic electrons can be precipitated by the nonresonant interaction between the electrons and EMIC waves, which is suggested by previous works.

Hertz Range Pulsations during Recovery Phase of the Magnetic Storm on September 7–8, 2017, and Relation between their Dynamics and Changes in the Parameters of the Interplanetary Medium

The shape and dynamics of an unusual disturbance in the Pc1 geomagnetic pulsation range recorded by ground-based induction magnetometers during the morning hours (03–06 MLT) on September 11, 2017, in the late recovery phase of a strong magnetic storm were analyzed in the context of changes in the parameters of the interplanetary medium. Pulsations were observed in the auroral and subauroral zones, as well as at midlatitudes, and had a complex structure in the form of multiplet “pearls” (1–1.5 Hz range) and two series of narrow-band bursts (2–3 Hz range) with a repetition period of ~5 and ~20 min. Pulsations in the form of a series of bursts are a rare event and are recorded mainly during the daytime hours. Comparison of the dynamics of Pc1 pulsations with the parameters of the interplanetary medium was carried out with data from the DSCOVR and THEMIS satellites. A change in the carrier frequency and intensity of multiplet pearls was a response to a jump in the plasma density of the solar wind. A series of bursts with a period of ~5 min could be initiated by a simultaneous increase in the solar-wind velocity and the By-component of the interplanetary magnetic field, which was observed ~40 min after the density jump. We associate bursts with a period of ~20 min either with the response of the magnetosphere to the short-term excursion of the daytime magnetopause to the Earth or with oscillations of a close period in the transition region ahead of the front of the density perturbation. The frequency, period, and amplitude of the pulsations are estimated.

Evening corotating patches (ECP) observed by DMSP/SSUSI

Evening corotating patches (ECP) are a special type of aurora, which occur at subauroral latitude. In the present work we have used the images observed by DMSP/SSUSI instruments to investigate the ECP in a global perspective. This study indicates that the ECP occur in the recovery phase of magnetic storms. The ECP were observed between 58° and 68° magnetic latitude (MLAT) in the evening sector between 16:00 and 20:00 magnetic local time (MLT). The ECP cororate with the Earth but they occur at same MLAT, this suggest that the source region related to ECP is inside the plasmasphere. Particle observations indicate that ECP are produced by energetic ions with energies above ∼20 keV, without much electron precipitations. We argue that the energetic ions producing ECP originates from the ring current, which is assumed to be filled with hot ions during the recovery phase of magnetic storms.

Modulation of the ionosphere by Pc5 waves observed simultaneously by GPS/TEC and EISCAT

Earlier studies demonstrated that the monitoring of the ionospheric total electron content (TEC) by global satellite navigation systems is a powerful method to study the propagation of transient disturbances in the ionosphere, induced by internal gravity waves. This technique has turned out to be sensitive enough to detect ionospheric signatures of magnetohydrodynamic waves as well. However, the effect of TEC modulation by ULF waves is not well examined as a responsible mechanism has not been firmly identified. During periods with intense Pc5 waves distinct pulsations with the same periodicity were found in the TEC data from high-latitude GPS receivers in Scandinavia. We analyze jointly responses in TEC variations and EISCAT ionospheric parameters to global Pc5 pulsations during the recovery phase of the strong magnetic storms on October 31, 2003. Comparison of periodic fluctuations of the electron density at different altitudes from EISCAT data shows that main contribution into TEC pulsations is provided by the lower ionosphere, up to ~150 km, that is the E-layer and lower F-layer. This observational fact favors the TEC modulation mechanism by field-aligned plasma transport induced by Alfven wave. Analytical estimates and numerical modeling support the effectiveness of this mechanism. Though the proposed hypothesis is basically consistent with the analyzed event, the correspondence between magnetic and ionospheric oscillations is not always perfect, so further studies need to be conducted to understand fully the TEC modulations associated with Pc5 pulsations.

Polar tongue of ionization (TOI) and associated Joule heating intensification investigated during the magnetically disturbed period of 1–2 October 2001

AbstractWe investigate storm‐enhanced density (SED) and polar tongue of ionization (TOI) over North America under southward Interplanetary Magnetic Field conditions. We focus on the 30 September to 1 October 2001 medium magnetic storm's recovery phase (Period 1) and on the last substorm (Period 2) of the following 2 October substorm series. We aim to study the SED‐TOI structure in the time frame of solar wind energy input to the magnetosphere‐ionosphere system and in terms of Joule heating. We utilize GPS total electron content maps tracking SED plume and polar TOI, and spectrogram images detecting polar rain and precipitation void and thus evidencing dayside merging. The variations of merging electric (E) field (EM) and its mapped‐down polar equivalent (EP), energy input efficiency (EIeff), and modeled Joule heating rate (QJoule) are monitored. Results show multiple Joule heating intensification points implying multiple energy deposition points at high latitudes where the magnetic pole was one of the preferred locations. During the higher EIeff (~1.5%) Period 2, the polar TOI was associated with a well‐defined strong QJoule intensification and with polar rain (or void) on the dayside (or nightside). During the lower EIeff (~0.5%) Period 1, only weak QJoule intensification occurred in the absence of both polar TOI and polar rain. We highlight the polar TOI's potential impact on the thermosphere. We conclude that (i) strong (EM ≈ 5 mV/m during Period 2) or weak (EM ≈ 0.5–2 mV/m during Period 1) EM facilitated energy deposition close to the magnetic pole and (ii) EIeff could be used as a diagnostic of the polar TOI's intensity.

Does the duration of the magnetic storm recovery phase depend on the development rate in its main phase? 2. A new method

In contrast to our previous work (Yermolaev et al., 2015), in which we used the magnetic storm recovery phase duration, the exponential time of the recovery phase of magnetic storms generated by three interplanetary driver types (CIR, Sheath, and ICME) is introduced in the present work. The dependence of these times on the storm development rate |Dstmin|/ΔT (where ΔT is the storm main phase duration) is studied. A similar physical result has been achieved despite the different data analysis method used: the times of the storm recovery and development rates correlate for storms induced by CIR and Sheath compression regions, and any relation between these parameters is absent for storms induced by ICME.

Intensity of the auroral electrojets during a recovery phase of magnetic storm

In this work, the effect of solar wind velocity on the development of magnetospheric and ionospheric disturbances is studied. It is shown that at high velocity of the solar wind during a recovery phase of magnetic storm the strong auroral activity characterized by the AE index is observed. In some cases during a recovery phase of magnetic storm the value of AE index is practically comparable with the value of AE index observed during the main phase of magnetic storm. When comparing time intervals of two magnetic storms during which the values of solar wind electric fields are approximately equal to each other, it is found that auroral electrojet intensity is stronger in that storm in which the solar wind velocity is higher.

Association of radiation belt electron enhancements with earthward penetration of Pc5 ULF waves: a case study of intense 2001 magnetic storms

Abstract. Geospace magnetic storms, driven by the solar wind, are associated with increases or decreases in the fluxes of relativistic electrons in the outer radiation belt. We examine the response of relativistic electrons to four intense magnetic storms, during which the minimum of the Dst index ranged from −105 to −387 nT, and compare these with concurrent observations of ultra-low-frequency (ULF) waves from the trans-Scandinavian IMAGE magnetometer network and stations from multiple magnetometer arrays available through the worldwide SuperMAG collaboration. The latitudinal and global distribution of Pc5 wave power is examined to determine how deep into the magnetosphere these waves penetrate. We then investigate the role of Pc5 wave activity deep in the magnetosphere in enhancements of radiation belt electrons population observed in the recovery phase of the magnetic storms. We show that, during magnetic storms characterized by increased post-storm electron fluxes as compared to their pre-storm values, the earthward shift of peak and inner boundary of the outer electron radiation belt follows the Pc5 wave activity, reaching L shells as low as 3–4. In contrast, the one magnetic storm characterized by irreversible loss of electrons was related to limited Pc5 wave activity that was not intensified at low L shells. These observations demonstrate that enhanced Pc5 ULF wave activity penetrating deep into the magnetosphere during the main and recovery phase of magnetic storms can, for the cases examined, distinguish storms that resulted in increases in relativistic electron fluxes in the outer radiation belts from those that did not.