Solar Wind Effects on the Transport of 3–10 MeV Cosmic‐Ray Electrons from Solar Minimum to Solar Maximum

2003 ◽  
Vol 594 (1) ◽  
pp. 552-560 ◽  
Author(s):  
S. E. S. Ferreira ◽  
M. S. Potgieter ◽  
D. M. Moeketsi ◽  
B. Heber ◽  
H. Fichtner
Keyword(s):  
Solar Wind ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Cosmic Ray ◽  
Wind Effects

scholarly journals Latitudinal and radial variation of >2 GeV/n protons and alpha-particles at solar maximum: ULYSSES COSPIN/KET and neutron monitor network observations

2003 ◽  
Vol 21 (6) ◽  
pp. 1295-1302 ◽  
Author(s):  
A. V. Belov ◽  
E. A. Eroshenko ◽  
B. Heber ◽  
V. G. Yanke ◽  
A. Raviart ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Neutron Monitor ◽  
Solar Minimum ◽  
Latitudinal Gradient ◽  
Solar Maximum ◽  
Cosmic Ray ◽  
Galactic Cosmic Rays ◽  
Alpha Particles ◽  
Polar Regions

Abstract. Ulysses, launched in October 1990, began its second out-of-ecliptic orbit in September 1997. In 2000/2001 the spacecraft passed from the south to the north polar regions of the Sun in the inner heliosphere. In contrast to the first rapid pole to pole passage in 1994/1995 close to solar minimum, Ulysses experiences now solar maximum conditions. The Kiel Electron Telescope (KET) measures also protons and alpha-particles in the energy range from 5 MeV/n to >2 GeV/n. To derive radial and latitudinal gradients for >2 GeV/n protons and alpha-particles, data from the Chicago instrument on board IMP-8 and the neutron monitor network have been used to determine the corresponding time profiles at Earth. We obtain a spatial distribution at solar maximum which differs greatly from the solar minimum distribution. A steady-state approximation, which was characterized by a small radial and significant latitudinal gradient at solar minimum, was interchanged with a highly variable one with a large radial and a small – consistent with zero – latitudinal gradient. A significant deviation from a spherically symmetric cosmic ray distribution following the reversal of the solar magnetic field in 2000/2001 has not been observed yet. A small deviation has only been observed at northern polar regions, showing an excess of particles instead of the expected depression. This indicates that the reconfiguration of the heliospheric magnetic field, caused by the reappearance of the northern polar coronal hole, starts dominating the modulation of galactic cosmic rays already at solar maximum.Key words. Interplanetary physics (cosmic rays; energetic particles) – Space plasma physics (charged particle motion and acceleration)

scholarly journals Solar cycle effect on geomagnetic storms caused by interplanetary magnetic clouds

2006 ◽  
Vol 24 (12) ◽  
pp. 3383-3389 ◽  
Author(s):  
C.-C. Wu ◽  
R. P. Lepping
Keyword(s):  
Solar Wind ◽  
Geomagnetic Storm ◽  
Solar Minimum ◽  
Geomagnetic Storms ◽  
Solar Maximum ◽  
Solar Wind Speed ◽  
Magnetic Clouds ◽  
Active Period ◽  
Quiet Period ◽  
Solar Wind Parameters

Abstract. We investigated geomagnetic activity which was induced by interplanetary magnetic clouds during the past four solar cycles, 1965–1998. We have found that the intensity of such geomagnetic storms is more severe in solar maximum than in solar minimum. In addition, we affirm that the average solar wind speed of magnetic clouds is faster in solar maximum than in solar minimum. In this study, we find that solar activity level plays a major role on the intensity of geomagnetic storms. In particular, some new statistical results are found and listed as follows. (1) The intensity of a geomagnetic storm in a solar active period is stronger than in a solar quiet period. (2) The magnitude of negative Bzmin is larger in a solar active period than in a quiet period. (3) Solar wind speed in an active period is faster than in a quiet period. (4) VBsmax in an active period is much larger than in a quiet period. (5) Solar wind parameters, Bzmin, Vmax and VBsmax are correlated well with geomagnetic storm intensity, Dstmin during a solar active period. (6) Solar wind parameters, Bzmin, and VBsmax are not correlated well (very poorly for Vmax) with geomagnetic storm intensity during a solar quiet period. (7) The speed of the solar wind plays a key role in the correlation of solar wind parameters vs. the intensity of a geomagnetic storm. (8) More severe storms with Dstmin≤−100 nT caused by MCs occurred in the solar active period than in the solar quiet period.

Variation with solar cycle of the diurnal variation of cosmic rays underground

1968 ◽  
Vol 46 (10) ◽  
pp. S784-S787 ◽  
Author(s):  
Victor H. Regener ◽  
Derek B. Swinson
Keyword(s):  
New Mexico ◽  
Diurnal Variation ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Cosmic Ray ◽  
Local Solar Time ◽  
The North ◽  
Primary Particles ◽  
Cosmic Ray Flux ◽  
Diurnal Maximum

The cosmic-ray diurnal variation has been observed with scintillator telescopes at a depth of 40 m.w.e. at Chacaltaya, Bolivia, since the last solar maximum, and at the same depth near Albuquerque, New Mexico, since the last solar minimum. During the solar maximum from 1958 to 1960 the amplitude of the diurnal variation was 0.3% for the Chacaltaya telescopes, but at solar minimum early in 1965 it was as low as 0.05%. Since that time, the amplitude has been steadily increasing, and it is now between 0.1% and 0.2% at both the Bolivia and the New Mexico stations.The telescopes measure the cosmic-ray flux from the north, south, east, and west directions, as well as from the vertical; and the various observed times of the diurnal maximum for these directions confirm the extraterrestrial nature of the anisotropy. The maximum occurs at approximately 15 h local solar time in the vertical telescopes. A study of the asymptotic directions of these telescopes for differing primary energies, and of the behavior of the phases of the diurnal variation at the two stations, gives indications of the energies of the primary particles responsible for the diurnal variation. The results are compared with the models of Axford and of Ahluwalia and Dessler.

scholarly journals Invariability of relationship between the polar cap magnetic activity and geoeffective interplanetary electric field

2011 ◽  
Vol 29 (8) ◽  
pp. 1479-1489 ◽  
Author(s):  
O. A. Troshichev ◽  
N. A. Podorozhkina ◽  
A. S. Janzhura
Keyword(s):  
Solar Wind ◽  
Solar Activity ◽  
Electric Field ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Magnetic Activity ◽  
Polar Cap ◽  
Polar Caps ◽  
The Relationship ◽  
Wind Energy Input

Abstract. The PC (polar cap) index characterizing the solar wind energy input into the magnetosphere is calculated with use of parameters α, β, and φ, determining the relationship between the interplanetary electric field (EKL) and the value of magnetic activity δF in the polar caps. These parameters were noted as valid for large and small EKL values, and as a result the suggestion was made (Troshichev et al., 2006) that the parameters should remain invariant irrespective of solar activity. To verify this suggestion, the independent sets of calibration parameters α, β, and φ were derived separately for the solar maximum (1998–2001) and solar minimum (1997, 2007–2009) epochs, with a proper choice of a quiet daily variation (QDC) as a level of reference for the polar cap magnetic activity value. The results presented in this paper demonstrate that parameters α, β, and φ, derived under conditions of solar maximum and solar minimum, are indeed in general conformity and provide consistent (within 10 % uncertainty) estimations of the PC index. It means that relationship between the geoeffective solar wind variations and the polar cap magnetic activity responding to these variations remains invariant irrespective of solar activity. The conclusion is made that parameters α, β, and φ derived in AARI#3 version for complete cycle of solar activity (1995–2005) can be regarded as forever valid.

The solar wind: from solar minimum to solar maximum

2001 ◽  
Vol 27 (3) ◽  
pp. 471-479 ◽  
Author(s):  
John D. Richardson ◽  
Chi Wang ◽  
Karolen I. Paularena
Keyword(s):  
Solar Wind ◽  
Solar Minimum ◽  
Solar Maximum

scholarly journals Solar cycle variations of the energetic H/He intensity ratio at high heliolatitudes and in the ecliptic plane

2003 ◽  
Vol 21 (6) ◽  
pp. 1229-1243 ◽  
Author(s):  
D. Lario ◽  
E. C. Roelof ◽  
R. B. Decker ◽  
G. C. Ho ◽  
C. G. Maclennan ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Intensity Ratio ◽  
Energetic Particle ◽  
Solar Minimum ◽  
High Speed ◽  
Solar Maximum ◽  
Ecliptic Plane ◽  
Interplanetary Shocks ◽  
Interplanetary Physics

Abstract. We study the variability of the heliospheric energetic proton-to-helium abundance ratios during different phases of the solar cycle. We use energetic particle, solar wind, and magnetic field data from the Ulysses, ACE and IMP-8 spacecraft to compare the H/He intensity ratio at high heliographic latitudes and in the ecliptic plane. During the first out-of-ecliptic excursion of Ulysses (1992–1996), the HI-SCALE instrument measured corotating energetic particle intensity enhancements characterized by low values (< 10) of the 0.5–1.0 MeV nucleon-1 H/He intensity ratio. During the second out-of-ecliptic excursion of Ulysses (1999–2002), the more frequent occurrence of solar energetic particle events resulted in almost continuously high (< 20) values of the H/He ratio, even at the highest heliolatitudes reached by Ulysses. Comparison with in-ecliptic measurements from an identical instrument on the ACE spacecraft showed similar H/He values at ACE and Ulysses, suggesting a remarkable uniformity of energetic particle intensities in the solar maximum heliosphere at high heliolatitudes and in the ecliptic plane. In-ecliptic observations of the H/He intensity ratio from the IMP-8 spacecraft show variations between solar maximum and solar minimum similar to those observed by Ulysses at high heliographic latitudes. We suggest that the variation of the H/He intensity ratio throughout the solar cycle is due to the different level of transient solar activity, as well as the different structure and duration that corotating solar wind structures have under solar maximum and solar minimum conditions. During solar minimum, the interactions between the two different types of solar wind streams (slow vs. fast) are strong and long-lasting, allowing for a continuous and efficient acceleration of interstellar pickup He +. During solar maximum, transient events of solar origin (characterized by high values of the H/He ratio) are able to globally fill the heliosphere. In addition, during solar maximum, the lack of strong recurrent high-speed solar wind streams, together with the dynamic character of the Sun, lead to weak and short-lived solar wind stream interactions. This results in a less efficient acceleration of pickup He +, and thus a higher value of the H/He intensity ratio.Key words. Interplanetary physics (energetic particles, interplanetary shocks; solar wind plasma)

scholarly journals Cosmic rays, aerosol formation and cloud-condensation nuclei: sensitivities to model uncertainties

2011 ◽  
Vol 11 (8) ◽  
pp. 4001-4013 ◽  
Author(s):  
E. J. Snow-Kropla ◽  
J. R. Pierce ◽  
D. M. Westervelt ◽  
W. Trivitayanurak
Keyword(s):  
Cosmic Rays ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Cloud Condensation Nuclei ◽  
Cosmic Ray ◽  
Organic Aerosol ◽  
Test Cases ◽  
Primary Emissions ◽  
Cosmic Ray Flux ◽  
Aerosol Properties

Abstract. The flux of cosmic rays to the atmosphere has been reported to correlate with cloud and aerosol properties. One proposed mechanism for these correlations is the "ion-aerosol clear-air" mechanism where the cosmic rays modulate atmospheric ion concentrations, ion-induced nucleation of aerosols and cloud condensation nuclei (CCN) concentrations. We use a global chemical transport model with online aerosol microphysics to explore the dependence of CCN concentrations on the cosmic-ray flux. Expanding upon previous work, we test the sensitivity of the cosmic-ray/CCN connection to several uncertain parameters in the model including primary emissions, Secondary Organic Aerosol (SOA) condensation and charge-enhanced condensational growth. The sensitivity of CCN to cosmic rays increases when simulations are run with decreased primary emissions, but show location-dependent behavior from increased amounts of secondary organic aerosol and charge-enhanced growth. For all test cases, the change in the concentration of particles larger than 80 nm between solar minimum (high cosmic ray flux) and solar maximum (low cosmic ray flux) simulations is less than 0.2 %. The change in the total number of particles larger than 10 nm was larger, but always less than 1 %. The simulated change in the column-integrated Ångström exponent was negligible for all test cases. Additionally, we test the predicted aerosol sensitivity to week-long Forbush decreases of cosmic rays and find that the maximum change in aerosol properties for these cases is similar to steady-state aerosol differences between the solar maximum and solar minimum. These results provide evidence that the effect of cosmic rays on CCN and clouds through the ion-aerosol clear-sky mechanism is limited by dampening from aerosol processes.

HIGH-ALTITUDE COSMIC RAY MEASUREMENTS AT FORT CHURCHILL

1960 ◽  
Vol 38 (5) ◽  
pp. 638-641 ◽  
Author(s):  
I. B. McDiarmid ◽  
D. C. Rose
Keyword(s):  
Solar Activity ◽  
High Altitude ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Cosmic Ray ◽  
Geiger Counter ◽  
Low Energy ◽  
High Solar Activity ◽  
Energy Radiation ◽  
Cosmic Ray Intensity

Measurements with rocket-borne Geiger counters have been carried out at altitudes up to 250 km at Fort Churchill, Manitoba. The total primary cosmic ray intensity at a time near a solar maximum has been determined and compared with other measurements taken at times of high solar activity and also with other Geiger counter measurements obtained near a solar minimum. A low-energy radiation was observed whose intensity increased with altitude up to about 25% of the primary intensity at 250 km.

scholarly journals The heliospheric magnetic flux, solar wind proton flux, and cosmic ray intensity during the coming solar minimum

Space Weather ◽  
2014 ◽  
Vol 12 (7) ◽  
pp. 499-507 ◽  
Author(s):  
Charles W. Smith ◽  
K. G. McCracken ◽  
Nathan A. Schwadron ◽  
Molly L. Goelzer
Keyword(s):  
Solar Wind ◽  
Magnetic Flux ◽  
Solar Minimum ◽  
Cosmic Ray ◽  
Proton Flux ◽  
Solar Wind Proton ◽  
Cosmic Ray Intensity
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