22nd Solar Cycle Research Articles

Space weather: The effects on operations in space

The major solar-terrestrial perturbations that occurred during the 22nd solar cycle have increased our awareness of the effects of space weather. An overview of the causes of some of these disturbances and the ensuing difficulties for operations in space are described. These include problems associated with communications, navigation, solar cells, spacecraft electronics, satellite positions and radiation to manned space vehicles. Also discussed are the effects of the ever present galactic cosmic radiation. Examples of definitive problems that were encountered during specific time periods are presented.

Common characteristics of the active regions of strong proton flares

Common characteristics of nine active regions with strong proton flares in the 22nd solar activity cycle have been presented. Results show that the typical morphology of these active regions is a delta-type sunspot with a single multiple structure, in which there are many umbras with different magnetic polarities, packed tightly by a single penumbra. In these active regions, the rotating directions of the sunspot groups are nearly independent of their position on the solar disk. When the angle of rotation approaches the positive or the negative maximum, proton flares may occur in these active regions. After proton flares, sunspot groups rotate in the inverse direction because of the slack in the flux rope.

Solar modulation of dose rate onboard the Mir station.

Models of the radiation belts that are currently used to estimate exposure for astronauts describe the environment at times of either solar minimum or solar maximum. Static models, constructed using data acquired prior to 1970 during a solar cycle with relatively low solar radio flux, have flux uncertainties of a factor of two to live and dose-rate uncertainties of a factor of about two. The inability of these static models to provide a dynamic description of the radiation belt environment limits our ability to predict radiation exposures for long-duration missions in low earth orbits. In an attempt to add some predictive capability of these models, we studied the measured daily absorbed dose rate on the Mir orbital station over roughly the complete 22nd solar cycle that saw some of the highest solar flux values in the last 40 y. We show that the daily trapped particle dose rate is an approximate power law function of daily atmospheric density. Atmospheric density values are in turn obtained from standard correlation with observed solar radio noise flux. This correlation improves, particularly during periods of high solar activity, if the density at roughly 400 days earlier time is used. This study suggests the possibility of a dose- and flux-predictive trapped-belt model based on atmospheric density.

A comparative study of global ionospheric responses to three great magnetic storms

Based on a large data base from 69 ionosonde stations distributed worldwide a comparative study is made on the global behavior of ionospheric responses to three great magnetic storms occurring nearly at low and high activity phase of the 22nd solar cycle. Depending on the season of storn occurrence, the global morphology of the ionospheric response to major magnetic storm is very different. For the February 1986 storm, hemispheric asymmetry of storm effects is remarkable, and positive storm effects are dominant in the winter hemisphere. Instead, for the two magnetic storms taking place near equinox in 1989, longlasting decreases in Nm were observed in both hemispheres Large-scale TIDs propagating equatorward were seen during the main phases of the October 1989 magnetic storm at evening-night sector. On the other hand, short-lasting positive storm effects appearing as wave-like disturbances in Nm were observed during the primary main phase of the 1986 storm in winter hemisphere. They seem to originate near the equatorial region and travel polarward.

A statistical study of solar microwave fine structure events

This paper presents a statistical summary of microwave fine structure (FS) events recorded by Beijing Astronomical Observatory at 2840 MHz in 1991. The statistical analysis shows that the time scales are between tens and hundreds of ms for more than 67% of the events and the amplitudes are less than 200 sfu in more than 85% of the cases. We discuss the time scale and intensity of FS events and the difference in the occurrence rate between the 21st and 22nd solar cycles.

Proton spectra of the four remarkable gle in the 22nd solar cycle

The proton spectra of several large solar particle events in the 22nd solar cycle (namely for the enhancements on 29 September 1989, 19 October 1989, 24 May 1990 and 15 June 1991) were obtained within the wide energy range directly by experimental data without any advance model. The data from spacecraft measurements and the world network of neutron monitors have been used to analyse these events. All the obtained spectra indicate a similar behaviour in the low energy range but differ at high energies > 1 GeV. The proposed method allows us to define the times of the maximum increase depending n the particle energy. The time-energy dependencies together with the proton flux profiles at different energies and the obtained spectra might be used as a predictor for estimation of the radiation dose in the maximum of the event, as well as its behaviour.

The spectrum of cosmic ray variations during the 19th–22nd solar cycles

The data from the world-wide network of neutron monitors, ionization chambers, stratospheric and satellite observations of cosmic ray intensity are used to investigate the long-term cosmic ray modulation in the period 1937–1991. The rigidity spectrum of the long-term cosmic ray modulation is obtained for the period 1954–1991 in the 1–25 GV rigidity range. The generalized spectral forms are obtained for periods of high and low solar activity. The obtained energy spectrum and the energy spectrum of the primary cosmic rays observed on the ULYSSES near Earth in November 1990 are compared. A satisfactory accordance between these two spectra is found.

The energy spectra and other properties of the great proton events during 22-nd solar cycle

The proton spectra and their variations during the several large solar particle events in 22-nd solar cycle (29.09.89, 19.10.89, 24.10.89, 24.05.90 and 15.06.91) were obtained within the wide energy range. The data of spacecraft measurements and neutron monitors of the world-wide network have been used to analyse the energy and temporal dependencies of proton increases. All peak spectra reveal the similar behaviour in the low energy range and significantly differ at energy > 1 GeV.

Analysis of spike emission data at 2545/2645 MHz in the peak year of the 22nd solar cycle

We briefly discuss the observed features including the high flux density, short duration, narrow emission band, fast frequency drift, quasi-periodic oscillation and fast variation of polarized components, of 51 spike emission events observed at 2545/2645 MHz in the solar activity peak year, 1991 January–December, and carry out correlation analysis between these events and optical flares, magnetic field intensity and configuration of flare regions, and sunspot evolution types of active regions. In view of the fact that the observed and statistical characteristics of the spike emissions are very different from those of known types of solar radio burst and known solar radio components, we think that the spike emission in the peak years is probably a new type of radio burst excited by electron cyclotron maser instability under wave-particle resonance, or a new solar radio component.

A comparison of energetic solar proton events during the declining phase of four solar cycles (cycles 19–22)

Solar proton events having a flux of >10 MeV protons ≥10 [cm 2-sec-ster] −1 typically occur during the years around solar sunspot maximum. Using >10 MeV solar proton data acquired at the earth for the 19th–21st solar cycles we find that approximately one third of the events occur on the rising portion of the cycle, one third during a two-to-three year period after sunspot maximum, and one third during the remainder of the cycle. The 22nd solar cycles has been an exception with more than twice as many events during the two years following solar maximum as during the rising portion of the cycle. In addition, as of July 1994, there have been relatively few solar proton events during the final decline of cycle 22. A terminal episode of major solar proton events that typically occurs several years after solar maximum, such as those events of July 1961, August 1972 and April 1984 has not yet been observed during the 22nd cycle which, as of July 1994, now appears to be rapidly approaching solar minimum. A comparison will be made of the energetic solar proton events that occurred during the declining portion of the past three solar cycles with those that have occurred during the decline of the present 22nd solar cycle.

CIR-associated interplanetary abundances at high heliolatitudes: Comparisons with in-ecliptic obser vations

The relative (to He) abundances of Z > 4 elements measured during intervals of corotating interaction regions (CIRs) at mid-heliospheric latitudes (∼23° to ∼45° south) are compared to CIR-associated measurements from in-ecliptic spacecraft near 1 A.U. Three different published compilations of inecliptic CIR-associated abundances are used in the comparisons. We find the relative abundances at higher latitudes, measured during the declining phase of the present (22nd) solar cycle, to be less than those measured near 1 A.U. during approximately the same phase of the last (21 st) solar cycle. The results provide evidence for a decreasing efficiency of CIRs for interplanetary particle acceleration with increasing heliolatitude.

Cosmic-ray long-term variations due to the solar activity for the 22nd solar cycle

In order to be studied the cosmic-ray long-term modulation monthly cosmic-ray data of the Deep River and Hermanus Neutron Monitor Stations for the 22nd solar-cycle have been used. Examining the hysteresis phenomenon of these data with different solar, interplanetary and terrestrial parameters we have noticed some interesting characteristics for the last solar cycle. According to an established empirical model we have attempted to reproduce to a certain degree the long-term modulation of the galactic cosmic-rays. A comparison with previous solar cycles has been made with noteworthing results for the odd and even solar cycles.

Radiation risk of the crew members of the expeditions on the “Mir” station during the 22nd solar activity cycle

The radiation risk at the end of the flight was calculated for the members of the main expeditions on the “Mir” station. It was based on the absorbed dose dynamics data measured by the board dosimeter. The radiation damage models created for standards of the radiation safety of the space flights were used in the calculations. The analysis of the obtaned values of the risk and its dynamics for some cosmonauts are presented in the topic. The risk values ΔP are close to the limited levels given by equation of ΔP = 0.6·10·T −4, where T - is flight duration in months.

The influence of interplanetary shocks on solar protons measured in the stratosphere

Since the beginning of the 22nd solar cycle twenty solar proton events were observed by the regular balloon measurements of cosmic rays. Temporal changes of intensities and energy spectra of solar protons with energy 100+500 MeV were obtained. The strong influence of interplanetary shock waves on the proton flux characteristics near the Earth was observed. Possible effects of solar proton transport in the vicinity of shock fronts are discussed to explain the observational data.

Measurement of the cosmic ray proton and helium fluxes from 200 MeV nucl−1 to 100 GeV nucl−1 during the 1987 solar minimum

Abstract The galactic cosmic ray proton and helium spectra have been measured with a balloon-borne superconducting magnetic spectrometer over the energy range from 200 MeV nucl−1 to 100 GeV nucl−1 during the 1987 solar minimum between the 21st and 22nd solar cycle. The absolute fluxes were approximately equal to the highest fluxes observed at the previous solar minimum in 1977. Above 10 GV the observed spectra are represented by a power law in rigidity with spectral indices of 2.74± 0.02 for protons and 2.68 ± 0.03 for helium. The data are consistent with rigidity power law interstellar spectra modulated with the solar modulation parameter φ = 500 MV.

Solar proton events at the growth phase of the 22nd solar activity cycle.

Meteor satellite observations in March, August, September and October 1989 recorded intensive solar proton events which caused a disturbed radiation situation in the near-Earth space. The paper presents the results of analyzing flux and spectral characteristics of the events and their relation to heliogeophysical situation.

The program of global character research of solar-terrestrial system in 22nd solar cycle in China, an overview

The Program on Global Character Research of Solar-Terrestrial System in the 22nd Solar Cycle (22 Max) have been carried out since 1987 in the Chinese Academy of Sciences. The coherent observations and measurements of solar physical, space physical and geo-sciences's equipments and facilities are well coordinated to study the cause and effect relationships in the period of an important solar flare event. In the present paper, an overview of the program is given.

Effects of RFI on Solar Microwave Bursts Observed with Hightime Resolution

ABSTRACTSolar microwave burst observations with high time resolution (~ 1 ms) are important but difficult to make. It is shown by the experiments of radiometer at wavelength 21 cm on 1 ms time scale that some ultrafast time structures in microwaves, which includes spike impulses, switch-on and switch-off structures, etc., may not be from solar emission but from RFI (radio-frequency interference) or from radiometer itself. Because of the uncertainty at 21 cm and other several wavelengths, we suggest that joint observations of the solar microwave bursts on 1 ms time scale should be carried out on the peak years of the 22nd solar activity cycle.

Long and short term variation of the 10.7 cm solar flux. The photospheric granules and the Z�rich numbers

Based on diurnal values of the total radio-flux density at 10.7 cm as well as on corresponding Zurich numbers the relation giving the radio-flux as function ofR is established. The behaviour of low and high values ofR andF2800 during the time interval 1957–1976 is studied. Preliminary conclusions drawn by other investigators are confirmed. A prediction of the total radio-flux for the 22nd solar cycle is given.

The Fuzzy Classification of the Solar Cycle and the Prediction for the 22nd Solar Cycle

The Fuzzy Classification of the Solar Cycle and the Prediction for the 22nd Solar Cycle