摘要:

In this paper, we predict the next cycle's activity and improve the timing of solar cycle predictions. Dynamobased solar activity prediction techniques rely upon two properties inherent in the solar cycle: that solar magnetism oscillates between poloidal and toroidal components; and that there is a degree of “magnetic persistence” in dynamos, which in the case of the Sun, results in the dependence of many magnetic related quantities (activity related quantities) upon the amount of magnetism embedded below the Sun's surface. Using the SODA (SOlar Dynamo Amplitude) index as a measure of magnetic persistence, we predict that solar cycle #23 will reach a mean smoothed F10.7 peak of 182±30 solar flux units (sfu) and a mean sunspot number Rz of 138±30. This is particularly intriguing because the “folklore” is that odd cycles are larger than the preceding even cycle. Additionally, by tracking the equatorward march of solar activity, the timing of the cycle can be better estimated. From this, we estimate that the next solar maximum will occur near May, 2000

ISSN:0094-8276    

DOI:10.1029/96GL00451

年代:1996

数据来源: WILEY

摘要:

We propose the persistent presence of randomly fluctuating, large‐amplitude, long‐timescale wavy spiral magnetic fields in the solar wind at all heliographic latitudes. These Alfvénic fluctuations can be generated by gradual evolution of solar coronal holes or by interplanetary Kelvin‐Helmholtz instabilities occurring around the two conical interfaces at ∼±30° where strong wind shears appear quasi‐periodically during the solar minimum. Using this scenario, we offer interpretations for several recent high‐latitude observations of quasi‐periodic (i.e., ∼26.6 days) energetic particle and cosmic ray modulations from Energetic Particle Composition instrument and Cosmic Ray and Solar Particle Investigation sensor systems aboard

ISSN:0094-8276    

DOI:10.1029/96GL00477

年代:1996

数据来源: WILEY

摘要:

We studied the relation between the long‐term temporal evolution of galactic cosmic ray (GCR) intensity observed in neutron monitors at Earth‐which shows alternating peaks of different shape depending on the polarity of the general solar magnetic field‐, and the evolution of the solar coronal holes for the period 1967–1988. This period covers almost one complete solar magnetic (22‐yr) cycle. We found that GCR intensity correlates with the evolution of the size of polar coronal holes, which also exhibits alternating time profiles in positive and negative phases of the solar magne

ISSN:0094-8276    

DOI:10.1029/96GL00471

年代:1996

数据来源: WILEY

摘要:

We use instrumentation on SAMPEX and the Earth's field as a magnetic rigidity filter in a “double spectrometer” approach to measure the composition and energy spectra of anomalous cosmic rays (ACRs) with Z≥6. A “pure” sample of anomalous cosmic ray C, N, O, and Ne is obtained, with no significant evidence for other species. The bulk of ACRs are now known to be singly‐charged, and the geomagnetic filter allows their energy spectra to be measured to higher energies than before. The anomalous oxygen spectrum is found to extend to at least ∼100 MeV/nuc, which has implications for models of the acceleration

ISSN:0094-8276    

DOI:10.1029/96GL00423

年代:1996

数据来源: WILEY

摘要:

We investigate a low Mach number supercritical quasiperpendicular shock using a three‐dimensional hybrid code. We find an out‐of‐coplanarity whistler wave mode propagating upstream, with properties similar to those of the “upstream whistlers” observed in the vicinity of planetary shocks. We discuss the generation mechanism, which turns out to be driven by the free energy provided by reflecte

ISSN:0094-8276    

DOI:10.1029/96GL00453

年代:1996

数据来源: WILEY

摘要:

A feature‐based classification technique is applied to the analysis of solar wind properties upstream of the Earth to predict the occurrence, duration, and magnitude of magnetic structures that can cause large geomagnetic storms. Because this method is based on identifiable physical features, it is highly upgradable by either analyzing data or physical models. The formulation of the technique is discussed and is then applied to two relatively “simple” solar wind events leading to large storms. The introduction of additional features to classify more “complicated” events is discussed to illustrate the upgr

ISSN:0094-8276    

DOI:10.1029/96GL00472

年代:1996

数据来源: WILEY

摘要:

We present observations of plasma sheet thinnings in the dawn sector of the near‐Earth tail (8≤R<11 RE) recorded by Prognoz‐8 during 2 substorms with multiple intensifications. In one case (on 23 July 1981), prolonged substorm activity in the compressed magnetosphere (at ∼5nPa solar wind dynamic pressure) was related to persistent strongly southward (Bz=−15 nT) interplanetary magnetic field. Plasma sheet dropouts began ∼one hour after the main onset. Cold plasma populations (the low latitude boundary layer/mantle) were seen in a stretched magnetic configuration deep in the magnetosphere. There were signatures of local acceleration/heating of cold plasma above the retreating/expanding hot plasma sheet. In the case of 27 July 1981, the same phenomena were recorded at a low ∼1 nPa solar wind dynamic pressure. The distribution of the duration of total 13 plasma sheet dropouts was in the range of 1 to 15 minutes, with the majority of events lasting less than 5 minutes. Our data are complementary to the recent reports on GEOS‐2 and CRRES energetic particle dropouts in the

ISSN:0094-8276    

DOI:10.1029/96GL00309

年代:1996

数据来源: WILEY

摘要:

In a laboratory experiment modeling conditions in the auroral ionosphere, magnetic and density fluctuations are observed to grow spontaneously within a field aligned density depletion. The plasma has both cross‐field pressure gradients and magnetically field‐aligned currents. The magnetic fluctuations, identified as shear Alfvén waves, are coupled with the density fluctuations depending upon the plasma beta, β. The fluctuations exhibit a coherent eigenmode structure at higher β and evolve towards broadband Alfvén turbulence as β is lowered. We identify the cross field pressure gradient as the dominant driving source for the fluc

ISSN:0094-8276    

DOI:10.1029/96GL00302

年代:1996

数据来源: WILEY

摘要:

Using the DE 2 electric field data from 191 dawndusk passes, we have sought parameters that distinguish between the various polar ionospheric convection patterns for northward IMF. The passes were divided into the daytime and nighttime sectors, and categorized the convection into three convection patterns for each sector by focusing on flow having a horizontal scale of>150 km. The three daytime sector patterns are convection of reverse polarity, i.e., sunward at the highest latitudes and antisunward on both sides of the sunward flow region, irregular convection having multiple sunward and antisunward flow regions, and convection having a single antisunward flow region at the highest latitude, which is similar to the pattern for southward IMF. The IMF clock (BY/BZ) angle, the Earth's dipole tilt angle, and the IMF BX/BZangle measured from the dipole axis are the parameters that cause the difference in the three convection patterns. In the nighttime sector three similar convection patterns are identified. The occurrence of these patterns is controlled by the IMF clock angle. Thus, the convection pattern for northward IMF is very sensitive to the direction of the IMF. The magnetospheric sources for the convection patterns are discussed.

ISSN:0094-8276    

DOI:10.1029/96GL00452

年代:1996

数据来源: WILEY

摘要:

Digitized allsky images of auroral optical emissions, recorded by a low light level TV system at Sanae (70.3°S, 2.4°W, L=4.0), have been mapped onto the angular sensitivity functions of both a broad, single‐beam riometer and narrow beams of an imaging riometer. During the rising phase of a substorm before local magnetic midnight, on 11 May, 1992, the integrated optical intensities in the inner four beam directions of the 16‐beam imaging riometer followed each other fairly closely, while the absorptions showed marked spatially inhomogeneous distributions. Regions of ionospheric absorption appeared not to coincide spatially with regions of discrete optical structures, but were adjacent to these structures. A small step of ∼0.09 dB in absorption was observed shortly after onset of the substorm on 27 July, 1979, and again on 11 May, 1992, but before the sharp increase in absorption. This step in absorption may be due to highly enhanced E‐region electron temperatures arising from strong dc electric fields connected to auroral arcs. During the event of 9 June, 1991, which started with an SSC at 00:40 UT, enhancements in absorptions followed enhancements in optical emissions repeatedly a

ISSN:0094-8276    

DOI:10.1029/96GL00377

年代:1996

数据来源: WILEY