Morphological features of the Morphological features of the spectral resonance structures at spectral resonance structures at

different latitudesdifferent latitudes

N.V. SemenovaN.V. SemenovaPolar Geophysical Institute, Apatity, Russia

Examples of Spectral Resonance Structure (SRS) observed inSodankyla Geophysical Observatory (L ~ 5.2) during two

successive days

Examples of SRS observed atCrete (Greece, L~1.3 ) during three successive days

Examples of SRS observed inBarentsburg (Spitsbergen, L~15.2) during two successive days

Generation of the Ionospheric Alfven Resonator (IAR)

After Belyaev et al. (1985)

The existence of the IAR causes resonance features of the ionosphere reflection coefficient

0 1 2 3 4 5Frequency, H z

0.0

0.2

0.4

0.6

0.8

1.0

Ref

lect

ion

Coe

ffici

ent

F1

F2

Dependence of the frequency interval of IAR (F) on ionospheric parameters

The theory of IAR The theory of IAR predicts dependence of predicts dependence of the SRS characteristics the SRS characteristics on parameterson parametersof upper ionosphereof upper ionosphere

)(

)(

hLan2

kc

kf 4

1

F = f k + 1 - f k = )( hLan2c

w h e r e c i s v e l o c i t y o f l i g h t , L i s e f f e c t i v e t h i c k n e s s o ft h e F - l a y e r , h i s t h i c k n e s s o f t h e F - l a y e r m a x i m u m , n a

i s t h e A l f v e n r e f r a c t i v e i n d e x a t t h e h e i g h t o f t h e F -l a y e r m a x i m u m .

50e

N0H

4ca

n .~

w h e r e H 0 - m a g n e t i c f i e l d , – p l a s m a d e n s i t y , N e - t h ee l e c t r o n d e n s i t y .

Morphological features of the Morphological features of the Spectral Resonance StructuresSpectral Resonance Structures at at

mid-latitudesmid-latitudes

Nizhny Novgorod

Examples of magnetic variation spectra observed at mid-latitude in the nighttime and daytime in the years of solar

activity minimum

The total number of observation The total number of observation days in half-year intervals days in half-year intervals

Probability of the SRS observation in 6-month intervals during the solar activity cycle

Variation of the number of Variation of the number of sunspots during the solar sunspots during the solar activity cycle averaged activity cycle averaged

over 6 months over 6 months

Morphological features of the Morphological features of the Spectral Resonance StructuresSpectral Resonance Structures at high at high

latitudes latitudes

Sodankyla Geophysical ObservatorySodankyla Geophysical Observatory

Examples of Spectral Resonance Structure observed inSodankyla Geophysical Observatory during two successive days

012

012

012

012

012

F, H

z

012

012

012

0 - 3 U T

3 - 6 U T

6 - 9 U T

9 - 12 U T

12 - 15 U T

15 - 18 U T

18 - 21 U T

21 - 24 U T

June 95 June 96 June 97 June 98 June 99

The SRS frequencyThe SRS frequencyinterval (interval (F) depends onF) depends on: • local timelocal time• seasonseason• solar activitysolar activity

0

1

0

1

0

1

0

1

Pro

babi

lity

0

1

0

1

0

1

0

10 - 3 U T

3 - 6 U T

6 - 9 U T

9 - 12 U T

12 - 15 U T

15 - 18 U T

18 - 21 U T

21 - 24 U T

June 95 June 96 June 97 June 98 June 99

The SRS occurrence rateThe SRS occurrence ratedepends on:depends on:• local timelocal time• seasonseason• solar activitysolar activity

Morphological features of the Morphological features of the Spectral Resonance StructuresSpectral Resonance Structures at low at low

latitudes latitudes

Island of Crete, GreeceIsland of Crete, Greece

Examples of SRS observed atCrete (Greece, L~1.3 ) during three successive days

Dependence of SRS occurrence rate and frequency interval on UT

Mixed SRS

F2 F1

Morphological features of the Morphological features of the Spectral Resonance StructuresSpectral Resonance Structures at at

high latitudeshigh latitudes

Barentsburg, Spitsbergen

Examples of SRS observed inBarentsburg (Spitsbergen, L~15.2) during two successive days

The number of observation days and probability of SRS observation as a function of season

0

10

20

30

40

nu

mb

er

of d

ays

0.0

0.2

0.4

0.6

0.8

1.0

pro

ba

bili

ty

Jul 02 O ct 02 Jan 03 Apr 03 Jul 03 O ct 03 Jan 04

Dependence of the F on season 0 - 3 UT

3 - 6 UT

6 - 9 UT

9 - 12 U T

12 - 15 U T

15 - 18 U T

18 - 21 U T

21 - 23 U T

Jul 02 O ct 02 Jan 03 Apr 03 Ju l 03 O ct 03 Jan 04

0.00.40.8

0.00.40.8

0.00.40.8

0.00.40.8

0.00.40.8

0.00.40.8

F, H

z

0.00.40.8

0.00.40.8

The example of simultaneous observations of SRS in Lovozero and Barentsburg

10 October 2003

The example of simultaneous observations of SRS in Lovozero and Barentsburg

11 October 2003

0 1 2 3 4 5

0.0

0.5

1.0

Ref

lect

ion

Coe

ffici

ent

0 1 2 3 4 5Frequency, H z

0.0

0.5

1.0

Ref

lect

ion

Coe

ffici

ent

June 1995

D ecem ber 1995

June 1999

D ecem ber 1999

100 1000 10000 100000 1000000Electron D ensity, cm -3

0

500

1000

1500

2000

Alti

tude

, km

June 1995

Decem ber 1995

June 1999

Decem ber 1999

Model ionospheric profiles and calculated reflection coefficientsfor different conditions

Comparison of the observed and calculated SRS frequencies

Future plansFuture plans