Noise in wireless systems from solar radio bursts

Solar radio bursts were first discovered as result of their interference in early defensive radar systems during the Second World War (1942). Such bursts can still affect radar systems, as well as new wireless technologies. We have investigated a forty-year record of solar radio burst data (1960–1999) as well as several individual radio events in the 23rd solar cycle. This paper reviews the results of a portion of this research. Statistically, for frequencies f  1 GHz (near current wireless bands), there can be a burst with amplitudes >10³ solar flux units (SFU; 1 SFU = 10⁻²² W/m²) every few days during solar maximum conditions, and such burst levels can produce problems in contemporary wireless systems.     

Study of distribution functions of interplanetary particles accelerated at co-rotating interaction region at∼5A.U.

We report the results of a study of the 12-hour average distribution functions of high Z nuclei as measured over a 10-day interval on the Ulysses spacecraft at a helioradius of5.2 A.U. We use the good time and atomic mass resolution of the composition aperture of the HI-SCALE instrument to determine the form of the distribution functions for C, O, Ne, Mg, Si, and Fe over the energy range 0.5–16 MeV/nucl. We find that the distribution functions of these ions can be organized by characteristic velocities that have values ranging between2000–3500 km/sec over this interval.     

Tracing the magnetic topology of coronal mass ejection events by Ulysses/HI-SCALE energetic particle observations in and out of the ecliptic

In January 2000, the Ulysses spacecraft observed an ICME event at 43° S heliographic latitude and ∼ 4.1 AU. We use electron (E _e>38 keV) observations to trace the topology of the IMF embedded within the ICME. The still controversial issue of whether ICMEs have been detached from the solar corona or are still magnetically anchored to it when they arrive at the spacecraft is tackled. An in ecliptic ICME event is also presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

Oxygen and Iron Ions at High Heliolatitudes

The fluxes of O and Fe ions at high heliolatitudes measured by the HiScale instrument on Ulysses reflect the dynamical processes that affect the charged particle populations in the heliosphere. Both the O and Fe ions show more latitude dependence in the first (solar minimum) orbit to high southern heliolatitudes than during the second (solar maximum) orbit. The ion fluxes are larger during the solar minimum orbit; the flux levels are influenced by the occurrence of corotating interaction regions. The Fe/O abundance ratios are found to be similar at 1 AU and at high heliolatitudes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Studies of some statistics of the interplanetary magnetic field and implications for discrete modes

We present some results from a statistical study of the levels of the power spectrum of the interplanetary magnetic field as measured by the Ulysses spacecraft near the ecliptic plane between 1 and 5 AU. We conclude from the studies of the probability distributions of the power spectral levels that the interplanetary medium is not totally chaotic, but can sustain high percentages (21% to 30% for the examples shown here) of discrete, low frequency modes, probably of solar origin, over a long interval of time.     

Elemental abundances in corotating interaction regions at high solar latitudes

Throughout 1993, as the Ulysses spacecraft traveled from 23° to 45° south heliolatitude, the HI-SCALE instrument on the spacecraft measured a recurrent series of enhanced particle fluxes with a recurrence period of 26.5 days. These particles are accelerated from a background seed population by the corotating interaction regions (CIRs) associated with a southern solar polar coronal hole. Using the Wart detector telescope of the HI-SCALE instrument, we have analyzed the elemental abundances of C, N, O, and Fe relative to He for 0.5–4.0 MeV/nucl ions and Ne, Mg, and Si for 1.0–4.0 MeV/nucl ions in the CIRs. We compare the relative abundances to some previous measurements reported from 1 A.U. as well as with solar photosphere abundances. We note that HI-SCALE measurements of the heliolatitude dependence of the oxygen abundance and spectrum as reported by Lanzerottiet al. (1994) suggest that a substantial fraction of the seed population for the CIR-accelerated oxygen is likely to be the anomalous oxygen component of the cosmic rays.