Space weather effects have two links to research of energetic particles in space. First, the direct one, connected with the interaction of high energy cosmic particles including galactic, solar ...cosmic rays, as well as magnetospheric particles, with various materials as satellite systems, atmosphere, ionosphere, airplane systems, human body at high altitudes and in space. Second one, the indirect relations, is checking the relevance of possible forecasts of space weather phenomena according to the data of energetic particles both on the ground and on the satellites and space probes. We review few selected aspects of the second type of relations with references mainly to recent studies, namely (i) progress in description of selected quasi-periodicities in cosmic ray time series which are of potential use for space weather studies, (ii) status in the forecast of geoeffective and radiation storm alerts using signatures of ground-based observations, (iii) problem of relativistic electrons in the vicinity of Earth.
Spectral analysis of neutron monitors and muon telescope daily averages counts shows a significant higher harmonic (∼9 day) of the 27 day variation of galactic cosmic rays (CRs). This ...quasiperiodicity is also present in the time series of daily averages of the product of interplanetary magnetic field magnitude and the square of solar wind speed (BV2). The wavelet spectrum density of the third harmonic of the 27 day variation of CRs is weakly correlated with the quantity BV2. This result reflects the coupling between galactic CR modulation and interplanetary parameters.
Key Points
Nine day periodicity is evident in the spectra of galactic cosmic rays
Nine day periodicity is also evident in the spectra of the quantity BV2
Coupling between galactic cosmic ray modulation and interplanetary parameters
Galactic cosmic rays (GCRs) are energetic, charged particles coming from outside the solar system. These particles encounter an outward-moving turbulent solar wind with cyclic magnetic-field ...fluctuations when entering the heliosphere. This causes convection and diffusion in the heliosphere. The GCR counts detected by the ground-based neutron-monitor stations show intensity changes with a fluctuation of ∼ 11 years and are anti-correlated with the sunspot numbers with some time lags. GCRs experience various types of modulation from different solar activity features and are important components of space weather. The previous solar cycle, Cycle 23, has shown anomalous behavior with a prolonged deep minimum, which was characterized by a record-setting high Galactic cosmic-ray flux observed at Earth. Solar Cycle 24 started much later than expected and progressed sluggishly toward its maxima. In this paper, we study the heliospheric modulation and intermediate-term periodicities of GCRs during the ascending phase of Cycle 24. We utilize simultaneous solar, interplanetary plasma, magnetic field, and geomagnetic activity data including the tilt angle of the heliospheric current sheet, and we study their relation with GCRs. The wavelet power spectrum of GCRs exhibits the presence of a variety of prominent short- and mid-term periodicities including the well-known Rieger and quasi-biennial periodicities. Possible explanations of the observed results are discussed in the light of numerical models.
With the goal of understanding the initiations of solar energetic particle (SEP) (MeV) and ground-level enhancement (GLE) (GeV) particles, we have studied relative timings at approximately the Sun ...between temporal evolutions of the particles and some electromagnetic radiation components representing flares and shocks. Results show that GLE onsets appear after flare prompt onsets and m-type II onsets, while the GLE-associated SEP onsets appear before the flare prompt onsets and m-type II onsets, thus specifying that the GLE-associated SEPs originate over the flare initial phases and get accelerated intensively over the flare prompt phases associated with coronal shocks. The flare initial phase is found always earlier than the coronal mass ejection (CME) initial phase, further justifying that the MeV particles are initiated particularly by the flare initial phases and are accelerated to GeV energetic by flare prompt phases associated with the coronal shocks. On the contrary, most of the non-GLE-SEP onsets appear well after the flare prompt onsets and m-type II onsets, demonstrating that the non-GLE-SEPs mostly generate over the most intense part of the flare rise phases associated with the coronal shocks. In another development, the relative timings of flare prompt onset and peak times to the m- and DH-type II onsets show that usually the m-type II bursts commence before the flare peaks and DH-type II bursts commence after the flare peaks, signifying that the coronal shocks manifested in m-type II bursts operate over the flare main acceleration phases, while the coronal shocks manifested in DH-type II bursts operate over the flare decay and/or CME propagation phases, thereby suggesting that the evolution of the particles accelerated at the flare main acceleration phases can be prolonged by the shocks associated with the CME propagation phases.
We present an overview of the ground-level enhancement (GLE 72) of the cosmic-ray intensity associated with the recent powerful solar flare SOL2017-09-10 (X-ray class X8.9) based on the available ...neutron monitor (NM) network observations and on data from the satellite GOES 13. The maximum increase at high-latitude near-sea-level NMs was
≈
6
–
7
%
(2-min averages), greater with better time resolution. A scatter plot of the maximum increase of the GLE
versus
solar energetic-particle (SEP, proton) flux
>
100
MeV
shows one of the softest spectra among GLEs relative to the SEP fluxes. However, at two high-mountain middle-latitude NMs the increase was
≈
1
%
, indicating the possibility of proton acceleration up to 6 GeV. Among the analyzed NM data the Fort Smith (FSMT) NM shows the earliest and the rather high increase between 16:06 – 16:08 UT. This indicates an anisotropy in the first phase of the GLE event. We calculate the acceptance cones of several NM stations at high latitudes and contours of pitch angles corresponding to the interplanetary magnetic field (IMF). When employing the available data we find that pion-decay
γ
-ray emission onset is in accordance with the time of the main flare energy release. The observed time interval of the impulsive burst of
>
100
MeV
γ
-ray emission probably corresponds to the time of a turbulent current sheet creation. The observed location of the impulsive burst pion-decay emission source coincides with the active region and the cusp-shaped structure. It seems that models assuming sub-relativistic proton production beginning in a turbulent reconnecting current sheet are consistent with the observations. If these particles were released from the Sun during a type III emission with a pion-decay maximum at
16
:
00
:
30
±
30
UT
, we get a plausible path length equal to
1.5
±
0.3
AU
of the particles responsible for the onset of the SEP event and GLE. The time lag of GLE 72 corresponds to the most probable interval of the time difference between GLE onset and main flare energy release. Although other scenarios are not excluded we attribute the protons that create the pion-decay emission and the protons responsible for the GLE and SEP event onset to a general population of accelerated particles.
Results of statistical study on relations between Forbush decreases (FDs) as observed at a middle-latitude, high mountain cosmic ray (CR) neutron monitor (NM), and the geomagnetic storms (GS), as ...well as on connections of FDs to interplanetary plasma structures, are presented. Study confirms and extends (until 2014) earlier results based on NM data from different geomagnetic cut-off positions and covering earlier periods, namely that FDs associated with halo coronal mass ejections (CMEs) and those related with the shocks correspond to higher amplitudes of FDs than those without the mentioned features.
Galactic cosmic rays (GCRs) encounter an outward-moving solar wind with cyclic magnetic-field fluctuation and turbulence. This causes convection and diffusion in the heliosphere. The GCR counts from ...the ground-based neutron monitor stations show intensity changes that are anti-correlated with the sunspot numbers with a lag of a few months. GCRs experience various types of modulation from different solar activity features and influence space weather and the terrestrial climate. In this work, we investigate certain aspects of the GCR modulation at low cut-off rigidity (
R
c
≈1 GV) in relation to some solar and geomagnetic indices for the entire solar cycle 23 (1996 – 2008). We separately study the GCR modulation during the ascending phase of cycle 23 including its maximum (1996 – 2002) and the descending phase including its minimum (2003 – 2008). We find that during the descending phase, the GCR recoveries are much faster than those of the solar parameters with negative time-lag. The results are discussed in light of modulation models, including drift effects and previous results.
Features and peculiarities of the cosmic ray intensity (CRI) and the geomagnetic activity, along with several solar plasma and interplanetary magnetic field, during the period 4–10 September 2017 are ...studied. The period was characterized by strong solar activity: Several solar flares occurred; several halo coronal mass ejections (CMEs) were ejected in space. In the near‐Earth interplanetary space, the CMEs driving shock(s) and sheath(s) were identified. At the Earth, strong Forbush decreases in CRI and geomagnetic storms were observed. Several large solar flares, one of them of very high X‐ray importance (X9.3) and three halo CMEs were detected in the solar atmosphere. Two shock‐associated interplanetary CMEs were observed during that interval in near‐Earth space; the latter and faster one arrived even as the ejecta of the earlier one was still crossing. Variations in interplanetary plasma and field parameters during, before, and after the Forbush decreases and geomagnetic storms that occurred during the considered period were examined. A detailed time‐lagged correlation analysis using data at three different temporal resolutions (hourly, 5‐min, and 1‐min) was also performed. Cross correlations of time series of CRI with geomagnetic activity during the period 4–10 September 2017 are computed. This cross‐correlation analysis between CRI variability (defined as the difference of the CRI count rate between the current and the previous time step) and the Dst indicates a delay of Dst by 3–4 hr.
Key Points
Forbush decreases and geomagnetic storms in the interval 4–10 September 2017 are studied
Simultaneous high‐resolution data of cosmic rays, Dst index, and solar wind are analyzed
Time lag correlation analysis is performed, and possibility of its use in space weather forecast is indicated
A propagation model of galactic cosmic protons through the heliosphere was implemented using a two-dimensional Monte Carlo approach to determine the differential intensities of protons during solar ...cycle 23. The model includes the effects due to the variation of solar activity during the propagation of cosmic rays from the boundary of the heliopause down to Earth's position. Drift effects are also accounted for. The simulated spectra were found to be in agreement with those obtained from experimental observations carried out by the BESS, AMS, and PAMELA collaborations. In addition, the modulated spectrum determined with the present code for the year 1995 exhibits the latitudinal gradient and equatorial southward offset minimum found by the Ulysses fast scan in 1995.
We studied the relation of cloud cover and cosmic rays during the period 1982–2010 measured at Lomnický štít (2634m above sea level, in the direction of 49.40°N, 20.22°E, geomagnetic vertical cut-off ...rigidity for cosmic ray ~3.85 GV). Daily means are used. It is seen that the correlations are insignificant for averaging shorter than about one year. We have found weak positive correlation for longer averaging times. Difference in distributions of cosmic ray intensity between the days with cloudless and overcast sky level at α=0.05 is found in the data. In addition to the experiments and clarification of physical mechanisms behind the relations studied here, longer time intervals and analysis at different sites with respect to cut-off rigidity and sea/continents along with the satellite data are important for progress in understanding the cosmic ray–cloud relation questions, at least from the point of view of empirical description of the dependencies.
•Weak correlation between cloud cover and cosmic ray intensity observed at a mountain.
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