Ionospheric storms at geophysically-equivalent sites – Part 1: Storm-time patterns for sub-auroral ionospheres

Abstract. The systematic study of ionospheric storms has been conducted primarily with groundbased data from the Northern Hemisphere. Significant progress has been made in defining typical morphology patterns at all latitudes; mechanisms have been identified and tested via modeling. At higher mid-latitudes (sites that are typically sub-auroral during non-storm conditions), the processes that change significantly during storms can be of comparable magnitudes, but with different time constants. These include ionospheric plasma dynamics from the penetration of magnetospheric electric fields, enhancements to thermospheric winds due to auroral and Joule heating inputs, disturbance dynamo electrodynamics driven by such winds, and thermospheric composition changes due to the changed circulation patterns. The ~12° tilt of the geomagnetic field axis causes significant longitude effects in all of these processes in the Northern Hemisphere. A complementary series of longitude effects would be expected to occur in the Southern Hemisphere. In this paper we begin a series of studies to investigate the longitudinal-hemispheric similarities and differences in the response of the ionosphere's peak electron density to geomagnetic storms. The ionosonde stations at Wallops Island (VA) and Hobart (Tasmania) have comparable geographic and geomagnetic latitudes for sub-auroral locations, are situated at longitudes close to that of the dipole tilt, and thus serve as our candidate station-pair choice for studies of ionospheric storms at geophysically-comparable locations. They have an excellent record of observations of the ionospheric penetration frequency (foF2) spanning several solar cycles, and thus are suitable for long-term studies. During solar cycle #20 (1964–1976), 206 geomagnetic storms occurred that had Ap≥30 or Kp≥5 for at least one day of the storm. Our analysis of average storm-time perturbations (percent deviations from the monthly means) showed a remarkable agreement at both sites under a variety of conditions. Yet, small differences do appear, and in systematic ways. We attempt to relate these to stresses imposed over a few days of a storm that mimic longer term morphology patterns occurring over seasonal and solar cycle time spans. Storm effects versus season point to possible mechanisms having hemispheric differences (as opposed to simply seasonal differences) in how solar wind energy is transmitted through the magnetosphere into the thermosphere-ionosphere system. Storm effects versus the strength of a geomagnetic storm may, similarly, be related to patterns seen during years of maximum versus minimum solar activity.

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Statistics of the largest geomagnetic storms per solar cycle (1844-1993)

Annales Geophysicae ◽

10.1007/s00585-997-0719-5 ◽

1997 ◽

Vol 15 (6) ◽

pp. 719-728 ◽

Cited By ~ 13

Author(s):

D. M. Willis ◽

P. R. Stevens ◽

S. R. Crothers

Keyword(s):

Statistical Analysis ◽

Solar Cycle ◽

Geomagnetic Storm ◽

Extreme Values ◽

Geomagnetic Storms ◽

Extreme Value ◽

Extreme Value Statistics ◽

Relative Dispersion ◽

Solar Cycles ◽

Aa Index

Abstract. A previous application of extreme-value statistics to the first, second and third largest geomagnetic storms per solar cycle for nine solar cycles is extended to fourteen solar cycles (1844–1993). The intensity of a geomagnetic storm is measured by the magnitude of the daily aa index, rather than the half-daily aa index used previously. Values of the conventional aa index (1868–1993), supplemented by the Helsinki Ak index (1844–1880), provide an almost continuous, and largely homogeneous, daily measure of geomagnetic activity over an interval of 150 years. As in the earlier investigation, analytic expressions giving the probabilities of the three greatest storms (extreme values) per solar cycle, as continuous functions of storm magnitude (aa), are obtained by least-squares fitting of the observations to the appropriate theoretical extreme-value probability functions. These expressions are used to obtain the statistical characteristics of the extreme values; namely, the mode, median, mean, standard deviation and relative dispersion. Since the Ak index may not provide an entirely homogeneous extension of the aa index, the statistical analysis is performed separately for twelve solar cycles (1868–1993), as well as nine solar cycles (1868–1967). The results are utilized to determine the expected ranges of the extreme values as a function of the number of solar cycles. For fourteen solar cycles, the expected ranges of the daily aa index for the first, second and third largest geomagnetic storms per solar cycle decrease monotonically in magnitude, contrary to the situation for the half-daily aa index over nine solar cycles. The observed range of the first extreme daily aa index for fourteen solar cycles is 159–352 nT and for twelve solar cycles is 215–352 nT. In a group of 100 solar cycles the expected ranges are expanded to 137–539 and 177–511 nT, which represent increases of 108% and 144% in the respective ranges. Thus there is at least a 99% probability that the daily aa index will satisfy the condition aa < 550 for the largest geomagnetic storm in the next 100 solar cycles. The statistical analysis is used to infer that remarkable conjugate auroral observations on the night of 16 September 1770, which were recorded during the first voyage of Captain Cook to Australia, occurred during an intense geomagnetic storm.

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Ionospheric dynamic and coupling processes during geomagnetic storms

10.5194/egusphere-egu2020-10498 ◽

2020 ◽

Author(s):

Chaosong Huang

Keyword(s):

Electric Fields ◽

Geomagnetic Storms ◽

Equatorial Ionosphere ◽

Ion Composition ◽

Hemispheric Differences ◽

Ion Density ◽

Ion Drift ◽

Low Latitudes ◽

Coupling Processes ◽

Ionospheric Dynamics

<p>Geomagnetic storms cause the largest disturbances in the ionosphere-thermosphere system. We use measurements with satellites and ground based radars to study storm-induced variations in ionospheric plasma drift, ion density, and ion composition at low latitudes. It is found that the storm-time change of ion drift velocity in the equatorial ionosphere can reach 200-300 m/s, the change of ion density can be one or two orders of magnitude, and the change of ion composition can be 50-80%. These extremely large changes in the ionosphere can last for several hours or even a few days during the main and recovery phases of magnetic storms. The longitudinal, latitudinal and hemispheric differences of storm-time ionospheric disturbances are analyzed from measurements of multiple satellites or radar chain. Very long, continuous penetration of interplanetary electric fields to the equatorial ionosphere for 6 or even 14 hours are observed, and the time when disturbance dynamo electric fields become dominant is identified. The interplay of penetration, shielding, and disturbance dynamo electric fields in the storm-time ionosphere will be addressed. Mechanisms responsible for storm-time ionospheric dynamics will be discussed.</p>

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Unusual migration of the prominence activities in recent solar cycles

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313010910 ◽

2013 ◽

Vol 8 (S300) ◽

pp. 161-167 ◽

Cited By ~ 2

Author(s):

Masumi Shimojo

Keyword(s):

Magnetic Field ◽

Solar Cycle ◽

Radial Velocity ◽

Northern Hemisphere ◽

Solar Maximum ◽

The Other ◽

Occurrence Rate ◽

Solar Cycles ◽

Global Magnetic Field ◽

Cycle 24

AbstractWe investigated the prominence eruptions and disappearances observed with the Nobeyama Radioheliograph during over 20 years for studying the anomaly of the recent solar cycle. Although the sunspot number of Cycle 24 is smaller than the previous one dramatically, the occurrence rate, size and radial velocity of the prominence activities are not changed significantly. We also found that the occurrence of the prominence activities in the northern hemisphere is normal from the duration of the cycle and the migration of the producing region of the prominence activities. On the other hand, the migration in the southern hemisphere significantly differs from that in the northern hemisphere and the previous cycles. Our results suggest that the anomalies of the global magnetic field distribution started at the solar maximum of Cycle 23.

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Prediction of Sunspot and Plage Coverage for Solar Cycle 25

The Astrophysical Journal ◽

10.3847/2041-8213/ac3663 ◽

2021 ◽

Vol 922 (1) ◽

pp. L12

Author(s):

Valentina Penza ◽

Francesco Berrilli ◽

Luca Bertello ◽

Matteo Cantoresi ◽

Serena Criscuoli

Keyword(s):

Solar Activity ◽

Solar Cycle ◽

Geomagnetic Storms ◽

Empirical Relationship ◽

Magnetic Activity ◽

Solar Cycles ◽

Spatial And Temporal Scales ◽

Weather Events ◽

Cycle 24 ◽

Odd Cycles

Abstract Solar variability occurs over a broad range of spatial and temporal scales, from the Sun’s brightening over its lifetime to the fluctuations commonly associated with magnetic activity over minutes to years. The latter activity includes most prominently the 11 yr sunspot solar cycle and its modulations. Space weather events, in the form of solar flares, solar energetic particles, coronal mass ejections, and geomagnetic storms, have long been known to approximately follow the solar cycle occurring more frequently at solar maximum than solar minimum. These events can significantly impact our advanced technologies and critical infrastructures, making the prediction for the strength of future solar cycles particularly important. Several methods have been proposed to predict the strength of the next solar cycle, cycle 25, with results that are generally not always consistent. Most of these methods are based on the international sunspot number time series, or other indicators of solar activity. We present here a new approach that uses more than 100 yr of measured fractional areas of the visible solar disk covered by sunspots and plages and an empirical relationship for each of these two indices of solar activity in even–odd cycles. We anticipate that cycle 25 will peak in 2024 and will last for about 12 yr, slightly longer than cycle 24. We also found that, in terms of sunspot and plage areas coverage, the amplitude of cycle 25 will be substantially similar or slightly higher than cycle 24.

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

Journal of Space Weather and Space Climate ◽

10.1051/swsc/2020063 ◽

2020 ◽

Vol 10 ◽

pp. 59

Author(s):

Zenon Nieckarz ◽

Grzegorz Michałek

Keyword(s):

Solar Activity ◽

Solar Cycle ◽

Geomagnetic Storms ◽

Low Frequency ◽

Slow Solar Wind ◽

Solar Cycles ◽

Geomagnetic Disturbances ◽

South Eastern ◽

Magnetic Pulsations ◽

Long Term Observation

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.

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Analytical Study of Severe and Great Geomagnetic Storms

Journal of Mountain Research ◽

10.51220/jmr.v16i2.2 ◽

2021 ◽

Vol 16 (2) ◽

Author(s):

Amita Raizada

Keyword(s):

Solar Cycle ◽

Northern Hemisphere ◽

Coronal Mass Ejections ◽

Solar Disk ◽

Analytical Study ◽

Geomagnetic Storms ◽

Western Region ◽

23Rd Solar Cycle

Severe and Great Geomagnetic storms are considered to be those which have Dst less than -200nT. The investigation years are January 1996 to December 2006, which refers to 23rd solar cycle. During this period, 18 Geomagnetic storms are observed. When there are maximum number of sunspots present at the solar disk, highest number of these Geomagnetic storms are observed, which is quite obvious. The Coronal Mass Ejections responsible for these storms depict latitudinal as well as longitudinal bias showing more inclination towards northern hemisphere and western region of the solar disk. These Coronal Mass Ejections are confined between 25 of the equator.

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Extreme Space-Weather Events and the Solar Cycle

Solar Physics ◽

10.1007/s11207-021-01831-3 ◽

2021 ◽

Vol 296 (5) ◽

Author(s):

Mathew J. Owens ◽

Mike Lockwood ◽

Luke A. Barnard ◽

Chris J. Scott ◽

Carl Haines ◽

...

Keyword(s):

Magnetic Field ◽

Solar Cycle ◽

Space Weather ◽

Extreme Events ◽

Solar Minimum ◽

Geomagnetic Storms ◽

Extreme Event ◽

Solar Maximum ◽

Solar Cycles ◽

Event Occurrence

AbstractSpace weather has long been known to approximately follow the solar cycle, with geomagnetic storms occurring more frequently at solar maximum than solar minimum. There is much debate, however, about whether the most hazardous events follow the same pattern. Extreme events – by definition – occur infrequently, and thus establishing their occurrence behaviour is difficult even with very long space-weather records. Here we use the 150-year $aa_{H}$ a a H record of global geomagnetic activity with a number of probabilistic models of geomagnetic-storm occurrence to test a range of hypotheses. We find that storms of all magnitudes occur more frequently during an active phase, centred on solar maximum, than during the quiet phase around solar minimum. We also show that the available observations are consistent with the most extreme events occurring more frequently during large solar cycles than small cycles. Finally, we report on the difference in extreme-event occurrence during odd- and even-numbered solar cycles, with events clustering earlier in even cycles and later in odd cycles. Despite the relatively few events available for study, we demonstrate that this is inconsistent with random occurrence. We interpret this finding in terms of the overlying coronal magnetic field and enhanced magnetic-field strengths in the heliosphere, which act to increase the geoeffectiveness of sheath regions ahead of extreme coronal mass ejections. Putting the three “rules” together allows the probability of extreme event occurrence for Solar Cycle 25 to be estimated, if the magnitude and length of the coming cycle can be predicted. This highlights both the feasibility and importance of solar-cycle prediction for planning and scheduling of activities and systems that are affected by extreme space weather.

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The Hemispheric Sign Rule of Current Helicity during the Rising Phase of Cycle 23

International Astronomical Union Colloquium ◽

10.1017/s0252921100064721 ◽

2000 ◽

Vol 179 ◽

pp. 303-306

Author(s):

S. D. Bao ◽

G. X. Ai ◽

H. Q. Zhang

Keyword(s):

Solar Cycle ◽

Southern Hemisphere ◽

Northern Hemisphere ◽

Active Regions ◽

Hemispheric Preference ◽

Current Helicity

AbstractWe compute the signs of two different current helicity parameters (i.e., αbestandHc) for 87 active regions during the rise of cycle 23. The results indicate that 59% of the active regions in the northern hemisphere have negative αbestand 65% in the southern hemisphere have positive. This is consistent with that of the cycle 22. However, the helicity parameterHcshows a weaker opposite hemispheric preference in the new solar cycle. Possible reasons are discussed.

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On the Prediction of Solar Cycles

Solar Physics ◽

10.1007/s11207-020-01760-7 ◽

2021 ◽

Vol 296 (1) ◽

Author(s):

V. Courtillot ◽

F. Lopes ◽

J. L. Le Mouël

Keyword(s):

Solar Activity ◽

Solar Cycle ◽

Transfer Function ◽

Singular Spectrum Analysis ◽

Activity Cycle ◽

Solar Activity Cycle ◽

Planetary Motion ◽

Data Sets ◽

Solar Cycles ◽

Jovian Planets

AbstractThis article deals with the prediction of the upcoming solar activity cycle, Solar Cycle 25. We propose that astronomical ephemeris, specifically taken from the catalogs of aphelia of the four Jovian planets, could be drivers of variations in solar activity, represented by the series of sunspot numbers (SSN) from 1749 to 2020. We use singular spectrum analysis (SSA) to associate components with similar periods in the ephemeris and SSN. We determine the transfer function between the two data sets. We improve the match in successive steps: first with Jupiter only, then with the four Jovian planets and finally including commensurable periods of pairs and pairs of pairs of the Jovian planets (following Mörth and Schlamminger in Planetary Motion, Sunspots and Climate, Solar-Terrestrial Influences on Weather and Climate, 193, 1979). The transfer function can be applied to the ephemeris to predict future cycles. We test this with success using the “hindcast prediction” of Solar Cycles 21 to 24, using only data preceding these cycles, and by analyzing separately two 130 and 140 year-long halves of the original series. We conclude with a prediction of Solar Cycle 25 that can be compared to a dozen predictions by other authors: the maximum would occur in 2026.2 (± 1 yr) and reach an amplitude of 97.6 (± 7.8), similar to that of Solar Cycle 24, therefore sketching a new “Modern minimum”, following the Dalton and Gleissberg minima.

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First results of low frequency electromagnetic wave detector of TC-2/Double Star program

Annales Geophysicae ◽

10.5194/angeo-23-2803-2005 ◽

2005 ◽

Vol 23 (8) ◽

pp. 2803-2811 ◽

Cited By ~ 29

Author(s):

J. B. Cao ◽

Z. X. Liu ◽

J. Y. Yang ◽

C. X. Yian ◽

Z. G. Wang ◽

...

Keyword(s):

Electromagnetic Wave ◽

Southern Hemisphere ◽

Northern Hemisphere ◽

Geomagnetic Storms ◽

Low Frequency ◽

Wave Detector ◽

Ion Cyclotron Waves ◽

Satellite Platform ◽

Ion Cyclotron ◽

First Results

Abstract. LFEW is a low frequency electromagnetic wave detector mounted on TC-2, which can measure the magnetic fluctuation of low frequency electromagnetic waves. The frequency range is 8 Hz to 10 kHz. LFEW comprises a boom-mounted, three-axis search coil magnetometer, a preamplifier and an electronics box that houses a Digital Spectrum Analyzer. LFEW was calibrated at Chambon-la-Forêt in France. The ground calibration results show that the performance of LFEW is similar to that of STAFF on TC-1. The first results of LFEW show that it works normally on board, and that the AC magnetic interference of the satellite platform is very small. In the plasmasphere, LFEW observed the ion cyclotron waves. During the geomagnetic storm on 8 November 2004, LFEW observed a wave burst associated with the oxygen ion cyclotron waves. This observation shows that during geomagnetic storms, the oxygen ions are very active in the inner magnetosphere. Outside the plasmasphere, LFEW observed the chorus on 3 November 2004. LFEW also observed the plasmaspheric hiss and mid-latitude hiss both in the Southern Hemisphere and Northern Hemisphere on 8 November 2004. The hiss in the Southern Hemisphere may be the reflected waves of the hiss in the Northern Hemisphere.

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