21 research outputs found
Solar parameters for modeling interplanetary background
The goal of the Fully Online Datacenter of Ultraviolet Emissions (FONDUE)
Working Team of the International Space Science Institute in Bern, Switzerland,
was to establish a common calibration of various UV and EUV heliospheric
observations, both spectroscopic and photometric. Realization of this goal
required an up-to-date model of spatial distribution of neutral interstellar
hydrogen in the heliosphere, and to that end, a credible model of the radiation
pressure and ionization processes was needed. This chapter describes the solar
factors shaping the distribution of neutral interstellar H in the heliosphere.
Presented are the solar Lyman-alpha flux and the solar Lyman-alpha resonant
radiation pressure force acting on neutral H atoms in the heliosphere, solar
EUV radiation and the photoionization of heliospheric hydrogen, and their
evolution in time and the still hypothetical variation with heliolatitude.
Further, solar wind and its evolution with solar activity is presented in the
context of the charge exchange ionization of heliospheric hydrogen, and in the
context of dynamic pressure variations. Also the electron ionization and its
variation with time, heliolatitude, and solar distance is presented. After a
review of all of those topics, we present an interim model of solar wind and
the other solar factors based on up-to-date in situ and remote sensing
observations of solar wind. Results of this effort will further be utilised to
improve on the model of solar wind evolution, which will be an invaluable asset
in all heliospheric measurements, including, among others, the observations of
Energetic Neutral Atoms by the Interstellar Boundary Explorer (IBEX).Comment: Chapter 2 in the planned "Cross-Calibration of Past and Present Far
UV Spectra of Solar System Objects and the Heliosphere", ISSI Scientific
Report No 12, ed. R.M. Bonnet, E. Quemerais, M. Snow, Springe
Study of sporadic-E clouds by backscatter radar
It is shown that swept-frequency backscatter
ionograms covering a range of azimuths can be used to study the dynamics of
sporadic-E clouds. A simple technique based on analytic ray tracing can be used
to simulate the observed narrow traces associated with Es
patches. This enables the location and extent of the sporadic-E clouds to be
determined. The motion of clouds can then be determined from a time sequence of
records. In order to demonstrate the method, results are presented from an
initial study of 5 days of backscatter ionograms from the Jindalee Stage B data
base obtained during March-April 1990. Usually 2â3 clouds were observed each
day, mainly during the evening and up to midnight. The clouds lasted from 1â4 h
and extended between 30°â80° in azimuth and 150-800 km in range. The clouds
were mostly stationary or drifted generally westward with velocities of up to 80
m sâ1. Only one cloud was observed moving eastward
DIAS effective sunspot number as an indicator of the ionospheric activity level over Europe
DIAS (European Digital Upper Atmosphere Server) effective sunspot
number â R12eff was recently introduced as a proxy of the ionospheric
conditions over Europe for regional ionospheric mapping
purposes. Although a pre-processing step for the real-time update of the
Simplified Ionospheric Regional Model (SIRM) to real-time conditions,
R12eff is available in real time by DIAS system (http://dias.space.noa.gr)
for independent operational use. In this paper we discuss the efficiency
of R12eff to specify ionospheric conditions over Europe. For this purpose,
the diurnal R12effâs reference pattern was determined on monthly
basis and for different solar cycle phases. The deviation of the real-time
R12eff estimates from the reference values, ÎR12eff was found to be
highly correlated with the foF2 storm-time disturbances, especially during
large scale effects indicating that DIAS-R12eff can provide a reliable
estimator of the ionospheric activity level over a substantial part of Europe
and a powerful tool for ionospheric specification applications.Published491-5121.7. Osservazioni di alta e media atmosfera3.9. Fisica della magnetosfera, ionosfera e meteorologia spazialeJCR Journalrestricte