Transcript 9.7 mHz - STIL-BAS

Study of Pi2 pulsations observed
from MAGDAS chain in Egypt
E. Ghamry1, 2, A. Mahrous 2, M.N. Yasin3, A. Fathy3 and K. Yumoto4
1- National Research Institute of Astronomy and Geophysics, NRIAG, Helwan.
2- Space Weather Monitoring Center (SWMC), Helwan University, Ain Helwan 11795,
Egypt.
3- Physics Department, Faculty of Science, Fayoum University
4- SERC, Kyushu University, Japan.
E-Mail: [email protected]
Outlines:[1]. Introduction
[2]. Analysis method
[3]. Studying the generation mechanism of Pi2 pulsation
observed at two low latitudinal stations through studying .
1. The local time frequency dependence.
2. The relation between the amplitude and the Local time.
3. the frequency variation of 10 successive Pi2 events
4. Studied the relation between the frequency of Pi2 pulsations, and
the level activity{ measured by Kp index }
5. Studied the properties of the Pi2 pulsation observed through the
main and the recovery phase of the magnetic storm in July/22/2009
[4]. Studied the propagation mechanism of Pi2 pulsations at two
low latitudinal stations.
[5]. Conclusion.
Introduction:Irregular Pi2 pulsations one of the most important Magnetohydromagnetic
waves ( indicator to the onset of the geomagnetic substorms at low latitudes )
observed on the earth’s surface, which had studied more extensively at high
latitudinal region, while still in debates at low latitudinal region, we had studied the
Pi2s observed at two latitudinal stations ( FYM and ASW ) in Egypt, includes to
MAGDAS Project ( one of the most extensive magnetometers distributed all over the
world ).
In the following study we tried to clarify the generation mechanism of Pi2s observed
at low latitude stations in Egypt.
Analysis method
• Period of analysis [ Nov 2008 to Oct 2009].
• Filtered data through the second order butter worth band pass filter
in the period range of the Pi2 (40:150) second [ Identify the
waveform and the amplitude ] of the Pi2 pulsations.
• Correlating the Pi2 with magnetic disturbance measured with AL
index ( Negative bays 120 nT)
• Estimating the frequency of Pi2 pulsations through two different
methods
• 1. Fast Fourier transformations
• 2. The wavelet power spectrum method. ( using meyer base
function).
• We determined the time delay through timing the maximum
energy H component.
The relation between the Number of events and the
average frequency variations
The dominant frequency ~ 9.7 mHz
Local time frequency dependence, H
Component.
For all 152 Pi2 events at
all Kp level activity.
Pi2 H component have the
frequency at both
stations
Solid line : Average hourly
variation
Max Frequency at 5 LT
Min frequency in [17:21 ]
Relatively high frequency [
21 : 24 }
Local time frequency variation for Low
level activity { Kp<3 }
Comparable frequency [0 :
16 ] LT.
Min frequency [ 17 : 20 ].
Max frequency 21 LT
The relation between Amplitude and
localtime [LT]
Max amplitude around local
midnight.
Pi2 pulsations at both
stations have insignificant
difference in amplitude
Pi2 at both stations has the
same waveform .
The last result suggest two possible generation mechanism.
Plasmapause surface waves due to local time frequency
dependence, or the Cavity Resonance (
Magnetospheric/ Plasmaspheric ).
Pi2 observed have the following characteristics
1. The same waveform.
2. The same periodic oscillation
To suggest one of them we have to investigate if Pi2s is a
global event.
If global Pi2 has a discrete frequency, with the last two
condition, it may be generated from cavity mode
resonance.
Successive pi2 events
Fast Fourier
Transformation
(FFT)
3 successive Pi2 events with Kp=1, the most right column show the dominant frequencies 11.7 , 12.7 and
11.7 mHz respectively for the three successive events, the upper panel show the raw data H component ,
the middle left panel show the filtered data in the Pi2 range and the bottom panel show the wavelet power
spectrum through 24-12-2008 FYM station.
Estimation of the frequency of pi2 pulsations
through wavelet power spectrum are 9.7 and
11.7 mHz respectively, through 20-2-2009 for
kp=1, for both FYM and ASW station, the color
code illustrate the power amplitude.
frequency of both events are 11.7 and 13.7 mHz
respectively, the panels from top to bottom show the
following (i). AE and AL index, (ii) Pi2 at FYM station,
(ii). Pi2 at ASW station, (iii)wavelet power spectrum
frequency vs UT for 27-3-2009, the color code illustrate
the power amplitude.
Successive Pi2 events observed through our data analysis
The
Successive events included in the discussion
Date
Frequency of the first event
(mHz)
Frequency of the second event
(mHz)
24-12-2008. fig(6a)
11.7
12.7
27-3-2209. fig(6c)
11.7
13.6
30-5-2009. fig(6d)
7.8
8.7
20-2-2009. fig(6b)
9.7
11.7
The successive Pi2 events do not included in the discussion ( included in our analysis )
Date
LT1
LT2
F1(mHz)
F2(mHz)
22-11-2008
16.77
17.75
9.7
13.6
28-11-2008
19.66
20.22
9.7
12.7
26-12-2008
22.4
23
10.7
11.7 (no activity)
7-2-2009
16.27
17.1
9.7
11.7
14-2-2009
0.1
0.9
11.7
13.6
13-3-2009
23
23.5
11.7
13.8
Events showed similar frequency for successive events
5-3-2009
5.7
5.9
11.7
11.7 nega
9-3-2009
13.4
14.1
9.7
9.7
2-7-2009
10.5
10.88
9.7
9.7
3-7-2009
13.8
14.37
7.8
7.8
28-9-2009
3.2
3.58
12.7
12.7
Comparing the frequency of Pi2 events at the dawn and the duskside, have the following
conditions
1. the same level activity
2. the maximum density =18 Cm-3
Precluded the FLR,
and Plasmapause
surface waves
Dawnside Date
Duskside Date
Kp level
Frequency
26-6-2009
26-11-2008
2
10.7
23-11-2008
24-12-2008
-2
11.7 and 10.7
Frequency Kp level activity dependence
Preclude FLR
Case study through magnetic storm
July/22/2009
The magnetic field and solar wind parameters
are. Vsw= 443.6 Km/S
Kp =6 in the main phase and Kp= 2 in the
recovery phase during the analysis interval of
Pi2 pulsation.
Dst index = -82 nT.
Through the main phase
.label (a) the AE and the AL index, (b) The Dst index (c) The raw H component at
ASW, (d) The filtered data in the range [ 40:150 ] second. and label (e) the wavelet
power spectrum, two Pi2 have 15.6mHz
Through the recovery phase
Discrete frequencies 12.7 , 15.6 and 12.7 mHz of three consecutive substorms
respectively,
Propagation of Pi2 pulsations
Pi2 observed at FYM and ASW station
during 20-2-2009,time difference for the
first and the second event are 11 and 13
second respectively
Pi2 observed at FYM and ASW station
during 8-3-2009,time difference for the
first and the second event are 25 and
23 second respectively
Time delay between FYM and ASW stations during
7-6-2009
Pi2 observed at FYM and ASW station during 7-6-2009,time
difference is 49 Second.
1. Always FYM station lagging from ASW by [
3:50 ] second in all local time sectors used in
our analysis [17 : 5 ] LT.
2. The time delay decrease with approaching
the local midnight.
3. The result is consistent with the model of
Uozumi et al (2009). And
GUO-HUA FAN et al (2000).
Conclusion
1. Pi2 pulsations H component have the same frequency,
waveform, and a comparable amplitude at both
stations.
2. Frequency of Pi2s showed geomagnetic activity
dependence
3. We suggest that the cavity mode resonance (
especially plasmaspheric) is a possible generation
mechanism
4. Always Pi2s observed at ASW lead FYM station.
Thank you
ありがとう