On the seasonal dependence of relativistic electron fluxes

Kanekal, S.; Baker, D. N.; McPherron, R. L.

doi:10.5194/angeo-28-1101-2010

Cited by 16 publications

(22 citation statements)

References 21 publications

(20 reference statements)

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“…These results differ from previous ones reported in (Kanekal et al, 2010). Analyzing SAMPEX electron flux data, they found a more prominent role for the RM effect.…”

Section: Discussioncontrasting

confidence: 99%

“…Note that if the peaks and valleys times expected for the equinoctial mechanism are shifted forward 4 days as in (Kanekal et al, 2010), the fluence times of maxima/minima fall into the equinoctial uncertainty interval. This time shift was attributed by Li et al (2001) and Kanekal et al (2010) to finite solar wind speed (∼ 440 km s −1 ).…”

Section: Dates Of Maxima and Minimamentioning

confidence: 99%

“…They found that the fluxes were nearly three times higher at the equinoxes than at solstices which means a semiannual modulation in these measurements (McPherron et al, 2009). Moreover, SAMPEX observations were also used by Kanekal et al (2010) to study the dependence of the SAV in relativistic electrons with a wide range of L-shells covering the descending and ascending parts of a SC. Their results showed that the flux peaks were delayed about 30 days from the times of the nominal equinoxes during the descending phase.…”

Section: Introductionmentioning

confidence: 99%

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Semiannual variation of Pc5 ULF waves and relativistic electrons over two solar cycles of observations: comparison with predictions of the classical hypotheses

Poblet

Azpilicueta

Lam

2019

Preprint

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Abstract. Pc5 ULF (ultra-low frequency) waves can energize electrons to relativistic energies of > 2 MeV in geostationary orbits. Enhanced fluxes of such electrons can induce operational anomalies in geostationary satellites. The variations of the two quantities in time scales ranging from days to solar cycles are thus of interest in gauging their space weather effects over different time frames. In this study, we present a statistical analysis of two 11-year solar cycles (Cycle 22 and 23) of data comprising the daily relativistic electron fluence observed by GOES geostationary satellites and daily Pc5 power derived from auroral zone magnetic observatories in Canada. Firstly, an autocorrelation analysis is carried out, which indicates 27-day periodicity in both parameters for all solar phases, and such a periodicity is most pronounced in the declining and late-declining phase. Also, a 9-day and 13-day periodicity, though not present in all the years, are seen in some years. Then, a superposed epoch analysis is performed to scrutinize Semiannual Variation (SAV), which shows fluence near the equinoxes is one order of magnitude higher than near solstices and Pc5 power is 0.5 orders of magnitude higher near the equinoxes than near the solstices. We then evaluate three possible SAV mechanisms (which are based on the Axial, Equinoctial, and Russel & McPherron effect) to determine which one can best explain the observations. Correlation of the profiles of the observational curves with those of the angles that control each of the SAV mechanisms suggests that the Equinoctial mechanism may be responsible for the SAV of electron fluence while both the Equinoctial and the Russell & McPherron mechanisms are important for the SAV of Pc5 power. Comparable results are obtained when using functional dependencies of the main angles instead of the angles mentioned above. Lastly, superposed curves of fluence and Pc5 power were used to calculate least-square fits with a fixed semiannual period. Comparison of maxima and minima of the fits with those predicted by the three mechanisms shows that the Equinoctial effect better estimates the maxima and minima of the SAV in fluence while for the SAV in Pc5 power the Equinoctial and Russell & McPherron mechanisms predict one maximum and one minimum each.

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“…These results differ from previous ones reported in (Kanekal et al, 2010). Analyzing SAMPEX electron flux data, they found a more prominent role for the RM effect.…”

Section: Discussioncontrasting

confidence: 99%

Section: Dates Of Maxima and Minimamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Semiannual variation of Pc5 ULF waves and relativistic electrons over two solar cycles of observations: comparison with predictions of the classical hypotheses

Poblet

Azpilicueta

Lam

2019

Preprint

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show abstract

“…The Russell-McPherron effect associates the seasonal variation with the variation of the angle between the geocentric solar magnetospheric (GSM) equatorial plane and the solar equatorial plane [Russell and McPherron, 1973]. None of the three main causes alone, or any combination of them, can explain completely the observed seasonal variation of magnetospheric storms [Häkkinen et al, 2003;Cliver et al, 2000] or radiation belt energetic electrons [Kanekal et al, 2010;Vassiliadis et al, 2002]. The complete set of processes causing the [27] We found the largest number of substorms in winter during the declining solar cycle phase, the longest substorms in summer during sunspot maxima, and the most intense substorms in spring and fall during the declining solar cycle phase.…”

Section: Discussionmentioning

confidence: 99%

From space weather toward space climate time scales: Substorm analysis from 1993 to 2008

et al. 2011

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[1] Magnetic activity in the Northern Hemisphere auroral region was examined during solar cycles 22 and 23 (1993-2008). Substorms were identified from ground-based magnetic field measurements by an automated search engine. On average, 550 substorms were observed per year, which gives in total about 9000 substorms. The interannual, seasonal and solar cycle-to-cycle variations of the substorm number (R ss ), substorm duration (T ss ), and peak amplitude (A ss ) were examined. The declining phases of both solar cycles 22 and 23 were more active than the other solar cycle phases due to the enhanced solar wind speed. The spring substorms during the declining solar cycle phase (|A ss,decl | = 500 nT) were 25% larger than the spring substorms during the ascending solar cycle years (|A ss,acs | = 400 nT). The following seasonal variation was found: the most intense substorms occurred during spring and fall, the largest substorm frequency in the Northern Hemisphere winter, and the longest-duration substorms in summer. Furthermore, we found a winter-summer asymmetry in the substorm number and duration, which is speculated to be due to the variations in the ionospheric conductivity. The solar cycle-to-cycle variation was found in the yearly substorm number and peak amplitude. The decline from the peak substorm activity in 1994 and 2003 to the following minima took 3 years during solar cycle 22, while it took 6 years during solar cycle 23.

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“…Similar results have been reported by Fidani et al (2008) where the selected EBs from NOAA satellite time series exhibited peak values between May and August annually, while less markedly in December. Annual (Vassiliadis et al, 2002) and semiannual (Kanekal et al, 2010) modulations in electron flux were observed in the SAMPEX data, where northern summer and spring with autumn flux increased, respectively. The SAMPEX lowEarth polar orbit at an altitude of about 600 km and an inclination of 82 • (Baker et al, 1993) was similar to the DEME-TER orbit.…”

Section: Long-term Variation Features Of Ebs At Different Energy Bandsmentioning

confidence: 97%

Burst increases of precipitating electrons recorded by the DEMETER satellite before strong earthquakes

Zhang

Fidani²,

Huang

et al. 2013

Nat. Hazards Earth Syst. Sci.

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Abstract. This case study developed a method for data processing over six years, from 2004 to 2010, of 70 keV-2.3 MeV electrons recorded by the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite. Short time increases in electron counting rates, having 99 % probabilities of not being Poisson fluctuations, were statistically selected using geomagnetic invariant space and called electron bursts. Temporal series were analysed confirming the seasonal variations in low energy bands of 70-450 keV. Differently from previous results, the DEME-TER results exhibited two peaks of electron bursts: one in the period June-August and one in the period DecemberFebruary annually. Specifically, six earthquake cases are presented in detail having increases in electron burst number prior to events. Moreover, electron burst precipitation occurring before each strong earthquake of the entire period over the life of the satellite with M ≥ 7.0 was verified as having a probability greater than 97 % of not being of a statistical origin. Low energetic electrons in 70-330 keV resulted occurring more frequently near seismic activity than those observed in 330 keV-2.34 MeV energy bands at the satellite altitude in the ionosphere.

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On the seasonal dependence of relativistic electron fluxes

Cited by 16 publications

References 21 publications

Semiannual variation of Pc5 ULF waves and relativistic electrons over two solar cycles of observations: comparison with predictions of the classical hypotheses

Semiannual variation of Pc5 ULF waves and relativistic electrons over two solar cycles of observations: comparison with predictions of the classical hypotheses

From space weather toward space climate time scales: Substorm analysis from 1993 to 2008

Burst increases of precipitating electrons recorded by the DEMETER satellite before strong earthquakes

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