276,543 research outputs found
Relationship between frontal dust storms and transient eddy activity in the northern hemisphere of Mars as observed by Mars Global Surveyor
We have compiled a catalog of frontal dust storms in the northern hemisphere using Mars Orbiter Camera daily global maps spanning ~2.3 Martian years of Mars Global Surveyor (MGS) observations (from 1999 to 2003). The most vigorous frontal storms that flush dust to the low latitudes occur in early-mid fall and mid-late winter, away from the northern winter solstice. While many streaks are observed in the polar hood during the winter solstice period, no frontal dust storms are observed in the vicinity of the north polar region. We have also analyzed simultaneous MGS Thermal Emission Spectrometer (TES) temperature data and found statistically significant negative temperature anomalies associated with frontal storms. In the lowest scale height of the atmosphere, the geographical and seasonal distributions of temperature standard deviations associated with transient variations agree well with the distributions of frontal storms. The correlation deteriorates with increasing altitude, suggesting that lower-level temperature waves are associated with the frontal dust storms. Specifically, eastward traveling m = 3 waves with periods of 2–3 sols appear to be closely related to the development of flushing frontal storms
Severe storms
The role of jet streams in the development of severe storms was analyzed. Local variations of flow resulting from rapid changes of geostrophic velocity along the air trajectory or inertial instability can produce cold advection. An analysis of meso-network data for 1968 and 1969 was performed. Although inertial instability was present in the network, local deviations in wind direction and cold advection were not detected
Recovery phase of magnetic storms induced by different interplanetary drivers
Statistical analysis of Dst behaviour during recovery phase of magnetic
storms induced by different types of interplanetary drivers is made on the
basis of OMNI data in period 1976-2000. We study storms induced by ICMEs
(including magnetic clouds (MC) and Ejecta) and both types of compressed
regions: corotating interaction regions (CIR) and Sheaths. The shortest,
moderate and longest durations of recovery phase are observed in ICME-, CIR-,
and Sheath-induced storms, respectively. Recovery phases of strong ( nT) magnetic storms are well approximated by hyperbolic functions
with constant times for all types of drivers
while for moderate ( nT) storms profile can not
be approximated by hyperbolic function with constant because
hyperbolic time increases with increasing time of recovery phase.
Relation between duration and value for storms induced by ICME and
Sheath has 2 parts: and duration correlate at small durations while
they anticorrelate at large durations.Comment: 18 pages, 4 figures, 2 tables, submitted to JGR special issue
"Response of Geospace to High-Speed Streams
A Study of the Morphology of Magnetic Storms Great Magnetic Storms
Average characteristics are determined for 74 great magnetic storms
with sudden commencements that occurred in 1902-1945. The storm field is
resolved for different epochs of storm time into tv;o parts: (i) Dst, which
is independent of local time, that is, of longitude A, relative to the sun,
and (ii) DS, which depends on A . They are obtained, for each of the three
magnetic elements, declination, horizontal force, and vertical force, at
eight geomagnetic latitudes ranging from 80°N to 1°S. DS is harmonically
analyzed; the first harmonic component is shown to be the main component of
DS. The storm-time course of this component is compared with that of Dst;
DS attains its maximum earlier and decays more rapidly. The results of the
analysis of great storms are compared with those for weak and moderate
storms that were reported previously. Some characteristics of Dst change
with intensity. Except in magnitude, main characteristics of DS are independent
of intensity.The research reported in the document has been sponsored
by the Air Force Cambridge Research Center, Air Research
and Development Command, under Contract No. AF 19(604)-2163.LIST OF TABLES -- LIST OF FIGURES -- ABSTRACT -- 1. INTRODUCTION -- 2. OBSERVATORIES -- 3. STORM-TIME VARIATIONS : 3.1 Dst in the geomagnetic-north component, Hgm ; 3.2 Dst in the geomagnetic-east component, Egm ; 3.3 Dst in the vertical force Z -- 4. DISTURBANCE DAILY VARIATIONS -- 5. FIRST HARMONIC COMPONENT OF DS -- 6 . HIGHER HARMONIC COMPONENTS OF DS AND SD -- 7. COMPARISON OF Dst AND DS -- 8 . SEASONAL VARIATIONS IN Dst : 8.1 Seasonal variation in Dst(H); season d and season j ; 8.2 Seasonal variation in Dst(H); season e and season s -- 9. SEASONAL VARIATIONS IN DS -- 10. CONCLUSION -- 11. ACKNOWLEDGEMENTS -- REFERENCESYe
A Study of the Morphology of Magnetic Storms: Moderate Magnetic Storms
Some average characteristics are determined for 136 moderate magnetic
storms with sudden commencements that occurred during the interval
1902-1945. The average storm field is resolved for different
epochs of storm time st into Dst, independent of local time, that is, of
longitude X , relative to the sun, and into DS, that depends on X , Part
DS is expressed in terms of harmonic components with respect to X ,
and like Dst, the amplitudes and phases of these components, are functions
of st and of geomagnetic latitude. They are determined, for each
of the three magnetic elements, declination, horizontal force, and vertical
force, at eight geomagnetic latitudes ranging from 80*N to 1°S. In
the first, and main harmonic component of DS, its variations with respect
to storm time differs notably from that of Dst: its maximum is
attained earlier and its decay is more rapid. The storm -time changes
of the smaller harmonic components of DS have been less fully determined.
The average characteristics of moderate storms are compared
with those of weak storms.The research reported in the document has been sponsored by
the Air Force Cambridge Research Center, Air Research and
Development Command, under Contract No, AF 19(604)-1732.
AF 19(604)-1732
AFCRC-TR-57-295
AD 117-256LIST OF TABLES -- LIST OF FIGURES -- ABSTRACT -- 1. INTRODUCTION -- 2. THE OBSERVATORIES -- 3. THE STORM-TIME VARIATIONS : 3.1 Dst in the Geomagnetic-North Component, Hgm ; 3.2 Dst in the Geomagnetic-East Component, Egm ; 3.3 Dst in the Vertical Force -- 4. THE DISTURBANCE DAILY VARIATIONS -- 5. THE FIRST COMPONENT OF DS -- 6 „ THE HIGHER HARMONIC COMPONENTS OF DS AND SD -- 7. COMPARISON OF Dst AND DS -- 8 „ CONCLUSION : 8.1 The Intensity Index of Magnetic Storms ; 8.2 The Dst Variations ; 8.3 The DS and SD Variations ; 8.4 Future Plans -- 9. ACKNOWLEDGEMENTS -- REFERENCESYe
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