Intense Geomagnetic Disturbances Research Articles

Observations of Mesospheric Gravity Waves Generated by Geomagnetic Activity

AbstractGravity waves (GWs) play an important role in the dynamics and energetics of the mesosphere. Geomagnetic activity is a known source of GWs in the upper atmosphere. However, how deep the effects of geomagnetic activity induced GWs penetrate into the mesosphere remains an open question. We use temperature measurements from the SABER/TIMED instrument between 2002 and 2018 to study the variations of mesospheric GW activity following intense geomagnetic disturbances identified by AE and Dst indices. By considering several case studies, we show for the first time that the GWs forced by geomagnetic activity can propagate down to about 80 km in the high latitude mesosphere. Only regions above 55° latitudes show a clear response. The fraction of cases in which there is an unambiguous enhancement in GW activity following the onset of geomagnetic disturbance is smaller during summer than other seasons. Only about half of the events show an unambiguous increase in GW activity during non‐summer periods and about one quarter of the events in summer show an enhancement in GWs. In addition, we also find that the high latitude mesopause is often seen to descend in altitude following onset of geomagnetic activity in the non‐summer high latitude region.

Simultaneous Global Ionospheric Disturbances Associated With Penetration Electric Fields During Intense and Minor Solar and Geomagnetic Disturbances

AbstractA new observational phenomenon, named Simultaneous Global Ionospheric Density Disturbance (SGD), is identified in GNSS total electron content (TEC) data during periods of three typical geospace disturbances: a Coronal Mass Ejection‐driven severe disturbance event, a high‐speed stream event, and a minor disturbance day with a maximum Kp of 4. SGDs occur frequently on dayside and dawn sectors, with a ∼1% TEC increase. Notably, SGDs can occur under minor solar‐geomagnetic disturbances. SGDs are likely caused by penetration electric fields (PEFs) of solar‐geomagnetic origin, as they are associated with Bz southward, increased auroral AL/AU, and solar wind pressure enhancements. These findings offer new insights into the nature of PEFs and their ionospheric impact while confirming some key earlier results obtained through alternative methods. Importantly, the accessibility of extensive GNSS networks, with at least 6,000 globally distributed receivers for ionospheric research, means that rich PEF information can be acquired, offering researchers numerous opportunities to investigate geospace electrodynamics.

Correlations between space weather parameters during intense geomagnetic storms: Analytical study

We explore the correlation between different parameters of space weather events associated with intense geomagnetic disturbances that occurred during the solar cycles (SCs) 23 and 24 (1996–2019). The space weather events under this study are the Solar Flares (SFs), Coronal Mass Ejections (CMEs), Geomagnetic Storms (GSs), Solar Energetic Protons (SEPs) and Electrons (SEEs), respectively. The severity of the GSs is identified based on the Dst ⩽-100 nT and a list of 111 GSs with their associated space weather counterparts is obtained over the pre-selected time period. The utilized association procedure between the different space weather events is described and their observed properties are listed. For the performed analysis, Pearson correlation metrics is employed. The results are summarized and discussed.

Geomagnetic disturbances reduce heart rate variability in the Normative Aging Study

BackgroundSolar and geomagnetic activity (GA) have been linked to increased cardiovascular (CVD) events. We hypothesize that heart rate variability (HRV) may be the biological mechanism between increased CVD risk and intense geomagnetic disturbances (GMD). MethodsTo evaluate the impact of GA and intense GMD on HRV in 809 elderly men [age mean 74.5 (SD = 6.8)] enrolled in the Normative Aging Study (Greater Boston Area), we performed repeated-measures using mixed-effects regression models. We evaluated two HRV outcomes: the square root of the mean squared differences of successive normal-to-normal intervals (r-MSSD) and the standard deviation of normal-to-normal heartbeat intervals (SDNN) in milliseconds (ms). We also compared the associations between Kp and HRV in patients with and without comorbidities such as diabetes and coronary heart diseases (CHD). We used data on global planetary K-Index (Kp) from middle latitudes as a GA and GMD (>75th Kp) parameters from the National Oceanic and Atmospheric Agency's Space Weather Prediction Center. ResultsWe found a near immediate effect of continuous and higher Kp on reduced HRV for exposures up to 24 h prior to electrocardiogram recording. A 75th percentile increase in 15-hour Kp prior the examination was associated with a −14.7 ms change in r-MSSD (95 CI: −23.1, −6.3, p-value = 0.0007) and a −8.2 ms change in SDNN (95 CI: −13.9, −2.5, p-value = 0.006). The associations remained similar after adjusting the models for air pollutants over the exposure window prior to the event. In periods of intense GMD, the associations were stronger in patients with CHD and non-diabetes. ConclusionsThis is the first study to demonstrate the potential adverse effects of geomagnetic activity on reduced heart rate variability in a large epidemiologic cohort over an extended period, which may have important clinical implications among different populations.

Long-term observation of magnetic pulsations through the ELF Hylaty station located in the Bieszczady Mountains (south–eastern Poland)

Ground-based measurements of ultra- and extremely low-frequency waves (ULF/ELF) carried out in 2005–2016 (the 23rd and 24th solar cycle) at the ELF Hylaty station in Bieszczady Mountains (south–eastern Poland) were used to identify the days (360 days) in which magnetic pulsation events (MPEs) occurred. To reveal sources of MPEs at the Sun we considered their correlation with the basic indices describing solar activity. Our analysis, like earlier studies, did not reveal a significant positive correlation between the MPE detection rate and the sunspot numbers (SSN). On the other hand, we showed that MPEs are strongly correlated (correlation coefficient ≈0.70) with moderate (Dst < −70 nT) and intense (Dst < −100 nT) geomagnetic disturbances expressed by the Disturbance Storm Index (Dst). We recognized all sources of these geomagnetic storms associated with the considered MPEs. Only 44% of the MPEs were associated with storms caused by CMEs listed in the CDAW LASCO CME catalog. 56% of the MPEs were associated with storms caused by other phenomena including corotating interaction regions (CIRs), slow solar wind or CMEs not detected by LASCO. We also demonstrated that the CMEs associated with the MPEs were very energetic, i.e. they were extremely wide (partial and halo events) and fast (with the average speed above 1100 km s−1). CMEs and CIRs generally appear in different phases of solar cycles. Because MPEs are strongly related to both of these phenomena they cannot be associated with any phase of a solar cycle or with any indicator characterizing a 11-year solar activity. We also suggested that the low number of MPEs associated with CMEs is due to the anomalous 24 solar cycle. During this cycle, due to low density of the interplanetary medium, CMEs could easily eject and expand, but they were not geoeffective.

Large Magnetic Storm on September 7–8, 2017: High-Latitude Geomagnetic Variations and Geomagnetic Pc5 Pulsations

The features of daytime high-latitude geomagnetic variations and geomagnetic pulsations in the Рс5 range during the recent, large, two-stage magnetic storm of September 7–8, 2017 are studied. The discussed disturbances were observed at the recovery phase of the first stage of the storm after the interplanetary magnetic field (IMF) turned northward. It is shown that the large sign-alternating variations in Ву and Bz components of the IMF caused intense geomagnetic disturbances up to 300–400 nT with a quasi-period of ~20 min in the daytime sector of polar latitudes, probably in the region of the daytime polar cusp. These disturbances may have reflected quasi-period motions of the daytime magnetopause and may have resulted from nonlinear transformation of the variations in the interplanaterary magnetic field in the magnetosheath or in the magnetospheric entry layers. The appearance of high-latitude long-period variations was accompanied by the excitation of bursts (wave packets) of geomagnetic Pc5 pulsations. The onset of Pc5 pulsation bursts often coincided with a sudden northward turn of the IMF. It was discovered for the first time that the development of a “daytime polar substorm,” i.e., a negative magnetic bay in the daytime sector of polar latitudes, led to a sudden termination of the generation of geomagnetic Pc5 pulsations over the entire latitude range in which these oscillations were recorded before the appearance of the daytime bay.

Characterization of high-intensity, long-duration continuous auroral activity (HILDCAA) events using recurrence quantification analysis

Abstract. Considering the magnetic reconnection and the viscous interaction as the fundamental mechanisms for transfer particles and energy into the magnetosphere, we study the dynamical characteristics of auroral electrojet (AE) index during high-intensity, long-duration continuous auroral activity (HILDCAA) events, using a long-term geomagnetic database (1975–2012), and other distinct interplanetary conditions (geomagnetically quiet intervals, co-rotating interaction regions (CIRs)/high-speed streams (HSSs) not followed by HILDCAAs, and events of AE comprised in global intense geomagnetic disturbances). It is worth noting that we also study active but non-HILDCAA intervals. Examining the geomagnetic AE index, we apply a dynamics analysis composed of the phase space, the recurrence plot (RP), and the recurrence quantification analysis (RQA) methods. As a result, the quantification finds two distinct clusterings of the dynamical behaviours occurring in the interplanetary medium: one regarding a geomagnetically quiet condition regime and the other regarding an interplanetary activity regime. Furthermore, the HILDCAAs seem unique events regarding a visible, intense manifestations of interplanetary Alfvénic waves; however, they are similar to the other kinds of conditions regarding a dynamical signature (based on RQA), because it is involved in the same complex mechanism of generating geomagnetic disturbances. Also, by characterizing the proper conditions of transitions from quiescent conditions to weaker geomagnetic disturbances inside the magnetosphere and ionosphere system, the RQA method indicates clearly the two fundamental dynamics (geomagnetically quiet intervals and HILDCAA events) to be evaluated with magneto-hydrodynamics simulations to understand better the critical processes related to energy and particle transfer into the magnetosphere–ionosphere system. Finally, with this work, we have also reinforced the potential applicability of the RQA method for characterizing nonlinear geomagnetic processes related to the magnetic reconnection and the viscous interaction affecting the magnetosphere.

A Transient but Protracted Geomagnetic Anomaly in the Sudbury Basin Following Two Near-Contiguous Intense Geomagnetic Storms

During the maintained quiescence between solar cycle 23 and 24, two unusually intense (K-indices = 7) global geomagnetic disturbances separated by 6 days occurred. They were followed by a protracted increase of between 150 and 200 nT in the vertical component of our local magnetic field (Sudbury, Ontario). The duration of the variation anomaly was unusually long, about 3 weeks, before returning to baseline following a one week period of below average intensity characterized by approximately 50 min periodicities. We suggest this anomaly supports previous research that specific temporal patterns of increased global geomagnetic activity when matched with local impedance/reluctance of ore bodies created the condition for remarkable transient changes in the surface static intensity of magnetic fields.

Effects observed in the ionospheric F region in the east Asian sector during the intense geomagnetic disturbances in the early part of November 2004

The Sun was very active in the early part of November 2004. During the period of 8–10 November 2004, intense geomagnetic disturbances with two superstorms were observed. In a companion paper (hereinafter referred to as paper 1), the effects observed in the F region during the intense geomagnetic disturbances in the early part of November 2004 in the Latin American sector were presented. In the present paper, we investigate the effects observed in the F region during the intense geomagnetic disturbances in the early part of November 2004 in the east Asian sector. We have used the ionospheric sounding observations at Ho Chi Minh City (Vietnam) and Okinawa, Yamagawa, Kokubunji, and Wakkanai (Japan) in the present investigations. Also, GPS observations in the east Asian sector (several longitude zones) have been used to study the effect in the F region during the intense geomagnetic disturbances. The ion density versus latitudinal variations obtained by the DMSP F15 satellite orbiting at about 800 km altitude in the east Asian sector and the magnetic field data obtained at several stations in the Japanese meridian are also presented. Several important features from these observations in both the sectors during this extended period of intense geomagnetic disturbances are presented. The east Asian sector showed very pronounced effects during the second superstorm, which was preceded by two storm enhancements. It should be mentioned that around the beginning of the night on 10 November, ionospheric irregularities propagating from higher midlatitude region to low‐latitude region were observed in the Japanese sector. The most intense geomagnetic field H component in that sector was observed on 10 November at L = 2.8, indicating that the auroral oval and the heating got further to low latitudes and the ionospheric irregularities observed in the Japanese sector on this night are midlatitude ionospheric disturbances associated with the second superstorm. The absence of ionospheric irregularities in the Japanese sector during the 8 November superstorm suggests that the magnetosphere‐ionosphere system was possibly preconditioned (primed) when the second interplanetary structure impacted the magnetosphere.

Effects observed in the Latin American sector ionospheric F region during the intense geomagnetic disturbances in the early part of November 2004

The Sun was very active in the early part of November 2004. During the period of 8–10 November 2004, intense geomagnetic disturbances with two superstorms were observed. In this paper, we have investigated the generation and suppression of equatorial ionospheric irregularities and the daytime changes in the F region electron density in the Latin American sector during the period of intense geomagnetic disturbances. We present the ionospheric sounding observations carried out at Manaus and Sao Jose dos Campos, Brazil, during this geomagnetically disturbed period. Also, GPS observations obtained from several stations in Brazil, Argentina, and St. Croix, U.S. Virgin Islands, during the disturbed period are presented. During the main phase of the first superstorm, around the prereversal enhancement time (night of 7–8 November), prompt penetration of electric field was observed and the presence of equatorial ionospheric irregularities was detected from St. Croix, U.S. Virgin Islands (in the northern hemisphere) to Bahia Blanca, Argentina (in the southern hemisphere). The ionospheric sounding observations at Manaus indicate inhibition of prereversal enhancement on the nights of 9–10 and 10–11 November, possibly due to the disturbed thermospheric winds or disturbance electric fields. Virtually no phase fluctuations on the nights of 9–10 and 10–11 November were observed in the Latin American sector. During the daytime on 8 November, the vertical total electron content (VTEC) observations show a negative storm phase at Porto Alegre (Brazil) and Bahia Blanca (Argentina). Again during the daytime on 10 November, the VTEC observations show a negative storm phase from Brasilia (Brazil) to Bahia Blanca. These negative storm phases are associated with a decrease in the O/N2 ratio. During the daytime on 9 November, the VTEC observations show a positive storm phase extending from St. Croix to Porto Alegre, and again on 10 November, VTEC observations show a positive storm phase. These positive storm phases observed are possibly due to changes in large‐scale wind circulation and an increase in the O/N2 ratio.

Intersector disbalance of the large-scale open solar magnetic field fluxes, active and passive boundaries, and solar-terrestrial extrastorms

The dynamics (from rotation to rotation) of the absolute values of the large-scale open solar magnetic field fluxes in the four-sector field structure has been considered for the first time, using CRs 2032–2035 in July–October 2005 as examples. An important role of the ratio of the fluxes at the eastern and western sector boundaries (Φ E /Φ W ) is confirmed. As in the cases of the two-sector structure, Φ E /Φ W > 1 is typical of active rigidly corotating boundaries with intense sunspot formation, flares, and interplanetary and geomagnetic disturbances. A remarkable property of the considered structure was the presence of a rapidly increasing flux in an initially narrow sector and the flux interaction with a stable rigidly corotating sector in the zone of the main active longitudes, which caused an unexpectedly strong geoeffective long-range action of flares near the corresponding active boundary.

The thermospheric composition different responses to geomagnetic storm in the winter and summer hemisphere measured by “SZ” Atmospheric Composition Detectors

Three “SZ” Atmospheric Composition Detectors (ACDs) on board spacecraft “SZ-2”, “SZ-3” and “SZ-4” were launched on 10th January 2001, 26th March 2002 and 31st December 2002 separately. A large quantity of thermospheric composition data at the orbital altitude ranging from 330 to 362 km were collected from the in-situ measurement of ACDs. The spacecrafts’ lifetime was just in the second peak period of the 23rd solar cycle which includes two peaks and the solar activity value F 10.7 was from 89 to 228. During this period, several intense geomagnetic disturbances happened. Measurement results show that the most abundant neutral composition in the thermosphere at the orbital altitudes of “SZ” spacecrafts is atomic oxygen with an abundance varied around 60–90% corresponding to the variation of altitude, local time, solar activity and geomagnetic activity etc. It is also indicated that there were an abnormal N 2 density increase and O density decrease in the higher latitude areas during geomagnetic disturbance peaks, and these changes appeared unsymmetric for the south and north hemisphere of the earth.

Value of Historical Space Weather Events

The recent publication in this journal of a research paper on the 1859 solar storm (S. F. Odenwald and J. L. Green, Space Weather, 5, S06002, doi:10.1029/2006SW000262, 2007) demonstrates that revisiting historical events can be a useful way in which to gain an understanding of contemporary issues in space weather. The intense geomagnetic disturbances following the solar activity in late August–early September 1859, including the first observation of a white light flare by Richard Carrington, have long been recognized to be among the largest recorded in the past century and a half. Although the effect of auroras on electrical telegraph systems had first been noticed as early as 1847, it was the widespread disturbances in Europe and the eastern United States from the 1859 events that provided the impetus for engineers to work on mitigation strategies. The 1859 events also demonstrated the need for more fundamental understanding of the causes that could produce the “anomalous” currents on the telegraph systems. While reviewing Odenwald and Green's manuscript submission, I was prompted to take down my copy of George Prescott's History, Theory, and Practice of the Electrical Telegraph, published by Ticknor and Fields in 1860, the year following Carrington's flare event. The telegraph is a once-modern technology that is now quite obsolete. At the time, it was a communication marvel, and Prescott was moved not only to write about the technical details of building telegraph systems (wires and batteries and keys and receivers), but also to explain to the public the phenomena of electricity and magnetism. This included the recently discovered effect of induced currents by Faraday in 1832. One chapter of Prescott describes “Working telegraph lines with auroral magnetism” (that is, the operation of a telegraph line under the influence of only auroral activity). This chapter is “space weather” in the era of the most modern (and only) electrical technology of the time. Prescott outlined then-current ideas of the cause or causes of the aurora followed by vivid contemporary descriptions of the effects from induced currents in the lines of various telegraph systems in the late 1840s through the 1850s. These disturbances originated from the same physical processes that today produce disturbances in power system grids, long communication cables, and pipelines. These natural processes are also analogs of the induced currents that were generated by the electromagnetic pulse following the United States's Starfish Prime high-altitude nuclear explosion of 1962. The sizes of the induced currents that might be measured in a long grounded conductor depend upon the magnitude and nature of the fluctuating ionosphere currents and the conductivity of the ground below. An unknown in planning a new long-conductor route is the extremes of the space-induced currents that might occur over the route. Historical information in the form of actual data records from a few large geomagnetic events in the twentieth century have previously been used for this purpose. It is likely that a clever analysis could be made of the telegraph routes of the disturbance effects from the mid nineteenth century, and especially from the 1859 period, in order to provide rough estimates of induced Earth currents resulting from these geomagnetic events. Such information would add to the presently limited set of historical extremes currently available and would be another contribution by the 1859 event to contemporary space weather. Louis J. Lanzerotti is editor of Space Weather, a distinguished research professor at the New Jersey Institute of Technology, and a consultant at Alcatel-Lucent Technologies’ Bell Laboratories.

Application of Close Degree to Classified Prediction of Geomagnetic Disturbances

Using the close degree and membership function and comprehensive evaluation in fuzzy mathematics, in conjunction with the solar observation of CME and IPS observation for the interplanetary solar storms caused by CME, we present a close degree prediction method for geomagnetic disturbance events caused by coronal mass ejection (CME)~shock waves identified by IPS observation. Based on the analysis of 74 geomagnetic disturbance events caused by CME-shock waves identified by IPS observation during 1997~003, five clustering indices and their weighted fuzzy sets are constructed. Typical fuzzy sets of small, moderate, intense geomagnetic disturbance events are built based on comprehensive evaluation. By constructing the respective fuzzy set of each event, based on the close degree between the fuzzy set and typical fuzzy sets, the prediction for geomagnetic disturbance magnitudes caused by the events can be obtained. Main results are as follows: For the 74 geomagnetic disturbance events, the prediction accuracy is 53.3% for small geomagnetic disturbance, 100% for moderate geomagnetic disturbances, and 90.20% for intense geomagnetic disturbances. The average precision of this method is 84%. This method is an effective application of fuzzy mathematics to studying the geomagnetic disturbance.

Geomagnetic signatures during the intense geomagnetic storms of 29 October and 20 November 2003

Solar cycle 23 in its declining phase witnessed the most pronounced space weather events during October–November 2003. A series of powerful solar flares and associated geoeffective Coronal Mass Ejections (CMEs) travelling at ∼2000 km/s drove shock fronts that impacted the Earth's magnetic field consecutively on 29 and 30 October, resulting in intense geomagnetic disturbances during 29–31 October. Another intense geomagnetic storm activity occurred during 20–21 November, resulting from a solar flare that had an associated geoeffective CME travelling at a speed of ∼1100 km/s. Digital ground magnetic field measurements from the equatorial and low-latitude locations in the Indian longitude zone, in conjuction with the interplanetary solar wind and magnetic filed parameters, are used to study the characteristics of these storms. Maximum magnitude of the total magnetospheric energy injected into the magnetosphere during the mainphase of the three major storm amounts to approximately 4.5×10 13, 3.6×10 13, 2.8×10 13 W. Another salient feature brought out is the close correspondence between the magnitude of the peak of the southward component of the interplanetary magnetic field B z and the strength of the storm intensity as inferred from the D st and low-latitude digital magnetic records.

Extremely high speed solar wind: 29–30 October 2003

On 29–30 October 2003 the Solar Wind Electron Proton Alpha Monitor (SWEPAM) instrument on the Advanced Composition Explorer (ACE) spacecraft measured solar wind speeds in excess of 1850 km/s, some of the highest speeds ever directly measured in the solar wind. These speeds were observed following two large coronal mass ejection (CME) driven shocks. Surprisingly, despite the unusually high speeds, many of the other solar wind parameters were not particularly unusual in comparison with other large transient events. The magnetic field reached −68 nT, a large but not unprecedented value. The proton temperatures were significantly higher than typical for a CME in the solar wind at 1 AU (>107 K), but the proton densities were moderate, leading to low to moderate proton beta. The solar wind dynamic pressure was not unusual for large events but, when coupled with the large negative Bz, was sufficient to cause intense geomagnetic disturbances.

Irregular Geomagnetic Pulsations within 0.5-5 Hz Range at L-3-4.

At the Yakut chain stations in the subauroral zone (L ∼ 3-4) Pil pulsations within 0.5-5 Hz frequency range have been revealed by the active band-pass filters. They are observed during intense geomagnetic disturbances (K≥ 4) in the interval of night-dawn hours on a background of Pi 1 B and Pi 1 C, and can be accompaniedby auroral pulsations in this frequency range. Main spatial-temporal characteristics of the high-frequency geomagnetic pulsations are presented and their possible sources are discussed.

Observations of narrow microburst trains in the geomagnetic storm of August 4-6, 1972

Summary. In the intense geomagnetic disturbances of early August 1972, auroral zone microburst trains were observed at balloon altitude and found to be significantly narrower in burst width and spacing than microbursts found previously at the same site. These observations suggest that the spacing of microburst peaks, as well as their width, is related to variations in the power spectrum of a magnetospheric acceleration process rather than the bounce motions of electrons in the geomagnetic field or the modulation of electron precipitation by drift waves in magnetospheric plasma.