A brief introduction to Polar Cap PatchesA brief introduction to Polar Cap Patchesby Jøran Moen

•Chapter 4 from the compendium is essential to understand production, loss, and transport of ionospheric plasma!!

•Clouds of high electron density form near the cusp inflow region on theClouds of high electron density form near the cusp inflow region on the dayside. They form and enter the polar cap in association with magnetopause reconnection

Solar EUV ionization is the main production mechanism for high•Solar EUV ionization is the main production mechanism for high density electron patches. When they enter the polar cap they stay in sharp contrast low-density plasma there

•The patches are frozen into the plasma motion (ExB-drift), and convect with the polar cap twin cell flow from day to night.

•The patches can be observed by radar and by ground based opticsThe patches can be observed by radar and by ground based optics. Recombination of O+ gives rise to 630.0 and 557.7 nm emissions.

•The only way for these patches to exit the polar cap is due to tail ti th th th OCBreconnection; then they can cross the OCB.

OUTLINE:OUTLINE: • Decay in patch electron

density and airglowdensity and airglow• 630 nm airglow

observations in the18-06 MLT sector

• Combined all-sky and SuperDARN convectionSuperDARN convectionmaps

Neutralization of O+ and airglow• Key processes:

ONONO k ++ ++ 1

OOOO

ONONOk

k

+⎯→⎯+

+⎯→⎯+++

++

22

2

2

1

ν

α

hOO

OOeO

+→

+⎯→⎯++

*

*2

[ ]+≈ On airglow

• In the F-region:

[ ]≈ One

[ ]+≈ One

g

Neglecting production and transport in the continuity equation wehave:

[ ]O∂ +[ ] lt

O=

∂∂ +

i O+ th l t d it i t ll d b th l t li.e. O+ or the electron density is controlled by the loss term l

[ ] [ ] [ ]( )[ ][ ]

2221++−=

∂∂ +

OkNkt

OO

[ ][ ][ ] [ ] −

∂−=+

+

dt

t

O

O β

β[ ] [ ]

0

0

−=

+=+

enn

et

ee

OO

β

β

Decay of electron density/O+

where

[ ] [ ]2221 += OkNkβ2

300

20

1 100.8−

⎟⎠⎞⎜

⎝⎛×=k Teff

2

4.030017

2 100.2 − ⎟⎠⎞⎜

⎝⎛×=k Teff

2329.0 ⊥+= ETT neff

Core instrumentation for UiO patch studies:

LYRNYA

ARR

Polar cap patches:• Major source:

Solar EUV ionized plasmap

• Patch definition by density: Ne = 2 x Neo

• By airglow intensity: Recombination of O+

50R above 630nm background

• Horisontal scale 100-1000 km

• Altitude of Airglow emissions:~300 km

TEC image demonstrating transport of EUV ionized plasma that e tends into the polar cap (Foster et al 2005)plasma that extends into the polar cap (Foster et al., 2005)

The only way to exit patches from the polar the polar cap is by tailthe polar the polar cap is by tail reconnection

12 MLT

70

80

0618

MSP

24

Svalbard – is an ideal platform for studying airglow patches at night

12 MLT

High-density patches70

High density patches formed in the Canadian/ American cusp sector drift at

0618

80

cusp sector drift at us at night

MSP

24

Occurence rate of polar cap patches

Eight winters (1997-2005) of MSP data from Ny-Ålesund have been analyzed

43 nights, 333 events

About 60% of the patchesAbout 60% of the patches exit the polar cap from 22-01 MLT, but patches was observed in the entire MLT

f 18 00 05 00range from 18:00-05:00.12 MLT

70

80

0618

24

MSP

Moen et al., GRL2008

A new tool for studying tail-reconnection dynamics

Gulbrandsen et al. (Work in progress)

NOTE:NOTE:• Patches exit the polar cap in the entire MLT range of

tail reconnection (18-05 MLT)( )• All-sky and radar tracking of patches provides a new

tool to study tail reconnection dynamics. I.e. to observe how thet cross the OCB – the poleward border of the night-time auroral ovalnight-time auroral oval.

• As high density plasma clouds tend to be turbulent, they are an important space weather phenomenon for communication and navigation systems. See next lidslide.

• With the ICI-series of sounding rockets, UiO specializes on in-situ measurements of polar cap patches ICI-3 will be launched from Svalbard winterpatches. ICI 3 will be launched from Svalbard winter 2011, and ICI-4 is planned to fly over Svalbard near solar maximum in 2014.

Of relevance to satellite navigation

• Turbulence and irregularities in the ionosphere give rise to scintillations in the satellite to groundgive rise to scintillations in the satellite to ground signal

• The Total Electron Content (TEC) along the path of a GPS signal can introduce a positioning error ( upa GPS signal can introduce a positioning error ( up to 100 m)

• More severe in the arctic regions• The effects on GPS can be one of the most• The effects on GPS can be one of the most

important space weather phenomena for Norway as the Barents sea opens for offshore activities and the East-West passage is likely to open due to

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are needed to see this picture.

p g y psea ice meltdown

ICI-2

Investigation Investigation of Cusp I l i i

Universitetet i Uppsala i 1983

IrregularitiesUniversitetet i Uppsala i 1983