The effect of high energy electron precipitation in MLT (Mesosphere-Lower Thermosphere)

E. Turunen / IPY Heliosphere impact on geospace, Kick-off meeting, Feb 5-9, 2007, Helsinki

Sodankylä Geophysical Observatory

The effect of high energy electron precipitation in MLT (Mesosphere-

Lower Thermosphere)

E. TurunenSodankylä Geophysical Observatory,Sodankylä, Finland

See also related talks by Annika Seppälä and Pekka Verronen in this meeting



Some Atmosphericcoupling processes:

Introduction



• Chapman SEP conference 2004: ”We think we do understand the atmosphere...?”



Do we understand?• The connection between space weather

and Earth’s climate?



Do we understand?

• The effect of variable cosmic ray input on Earth’s atmosphere?

• The effect of hard X-rays during solar flares on Earth’s middle and upper atmosphere?

• The global effect of relativistic electron precipitation and its variability?



Do we understand?

• The effect of solar cycle variation in soft X-ray and EUV radiation forcing on Earth’s middle and upper atmosphere?

• The mid-term and short-term effects of such variation, due to day-to-day variability of solar activity?



Do we understand the impact of solar and magnetospheric energetic particles on the chemistry of the middle and upper atmosphere of Earth?



Particle precipitation causes:

• Increased energy deposition– Dynamic effects

• Increased ionisation– Conductivity variations– Radio wave propagation effects– Chemistry effects

• Increased dissociation– Chemistry effects

• Increased excitation



• Thermospheric NO might be carried down to the stratosphere, where it would enhance the background density of odd nitrogen and participate in the catalytic destruction of ozone [Siskind et al., 1997,Siskind, 2001 ].

• Mesospheric and stratospheric NO might be created in situ by very high energy particles

• As an example, Reid et al. [1991] give an example of 20% ozone decrease at the altitude of 45 km in response to solar proton events in late 1989



How do we monitor these effects?

• Ground-based networks– Magnetometers– All-sky cameras



Photometers andspectrometers



A network is better!



2-D reconstruction of an auroral arc



Radars and radio receivers• Ionospheric sounders

– Real time digital sounder network

• Coherent radars– STARE, CUTLASS

• Incoherent scatter radars– EISCAT UHF and VHF, ESR

• Satellite tomography– LEO satellites, GPS

• MF and HF radio propagation• VLF radio propagation• Riometers

– Imaging riometers, GLORIA-proposal



EISCAT Incoherent Scatter Radars in Tromsø and Svalbard

UHF radar

VHF radar



Finnish riometer network

• Riometers in Northern Scandinavia

• - continuous monitoring of total electron concentration during excessive ionisation

• IRIS, imaging riometer at Kilpisjärvi



Satellite tomography



Tomography across aurora !



Satellite measurements

• ENVISAT– GOMOS

• O3

• stratosphere-mesosphere

– MIPAS,• O3, Noy

• stratosphere

– SCIAMACHY• O3,Nox

• stratosphere-mesosphere

• Odin– OSIRIS

• O3

– SMR,• O3,NO,HO2

• EOS Aura– OMI– MLS



Experimental data to compare

• UARS– HALOE

• O3,NOy

• SNOE– UVS

• NO

• TIMED– SABER

• O3,NO,OH



Solar radiation control of chemistry

• Upper panel:– solar zenith angle

between 1300 and 1700 UT, Oct 23, 1989

• Middle panel– relative flux of UV light

(<318 nm) at 40-100 km

• Lower panel– relative flux of visible

light (<422 nm) at 40-100 km

(from P.Verronen et al., 2006)



Particle precipitation and ozone

When protons or electrons precipitate into atmosphere ions and secondary electrons are produced, also some NOx via dissociative ionization of N2. Ions and electrons react chemically and produce odd hydrogen, odd nitrogen and negative ions. This trio then affects ozone (loss) via catalytic reaction chains.



NO + O3->NO2 +O2

NO2 + O3->NO +2O2 OH + O->H + O2

H + O3->OH +O2

O2O

N2O2+N2

+

O+

O2N2

O2

H2O

O

H2O

NO+e

e

O4+

O2+ ( H2O)

N N(2D)

NO

OH H

HO3+ ( H2O)n

pp pp p

Particle precipitation

loss of ozone



Motivation• Particle precipitation in the upper atmosphere

affects odd nitrogen (N+NO+NO2) and odd hydrogen (H+HO+HO2)

• In polar night conditions, NO is long-lived and may be carried vertically down to lower altitudes and horisontally to lower latitudes

• Mesospheric and stratospheric NO might be created in situ by very high energy particles



Motivation

• Odd hydrogen and odd nitrogen destroy ozone

• Ozone is important in the radiation balance of the upper atmosphere

• Is this a mechanism to couple space weather variations to variations in Earth’s climate?



Several solar proton events were studied, in order to see the effects of increasing ionisation on ozone.Production/ Loss model is confirmed experimentally

Finnish work on Solar Proton Events (SPE)

(recent works by Verronen et al, Seppälä et al., Clilverd et al., Rodger et al.)



Seppälä et al., (2006)

SPE Jan 2005



Example application

• Ozone destruction during SPE Oct-Nov 2003

– quantitative model estimate confirmed by ENVISAT/ GOMOS measurements

• Verronen et al, (2005)



SIC model



SIC model



SIC model

• The Sodankylä Ion Chemistry Model (SIC) was applied first by Burns et al. [1991] in a study of EISCAT radar data, and thereafter by, e.g., Turunen [1993], Rietveld et al. [1996], Ulich et al. [2000], Verronen et al. [2002] and Clilverd et al. [2005]

• A detailed description of the original SIC model, in which only ion chemistry was considered, can be found in the work of Turunen et al. [1996].

• The latest version solves the concentrations of 63 ions, including 27 negative ions as well as 13 neutral species (O(3P), O(1D), O3, N(4S),

N(2D), NO,NO2, NO3, HNO3, N2O5, H, OH, and HO2)

• In this study also O2(1g) and H2O2 as unknowns.



• Altitude range is from 20 to 150 km, with 1-km resolution.

• Several hundred chemical reactions are taken into account.

• External forcing due to solar radiation, electron and proton precipitation, and galactic cosmic rays.

• The background neutral atmosphere is generated using the MSISE-90 model [Hedin, 1991] and tables given by Shimazaki [1984].

• The former provides altitude profiles of N2, O2, Ar, He, and temperature with 1-km resolution for any given set of time, geographic location, magnetic Ap index, and solar F10.7 flux.

SIC model cont.



• The latter provides concentrations of O2(1g), N2O, H2, H2O, H2O2, HNO2, HCl, Cl, ClO, CH3, CH4, CH2O, CO, and CO2 for noon and midnight conditions at altitudes 10, 15, 20, 25, 30, 45, 60, 80, and 100 km, which are then converted into altitude profiles of 1-km resolution by interpolation.

• For the 1-km Shimazaki-based profiles, interpolation with respect to solar flux is used to make the transition from day to night and vice versa.

• The concentrations of H2O and CO2 are calculated using fixed volume mixing ratio profiles, the default values are 5 ppmv (below 80 km) and 335 ppmv, respectively.

SIC model cont.



• The solar flux is estimated by the SOLAR2000 model [Tobiska et al., 2000], version 2.23.

• The scattered component of the solar Lyman-a flux is included using the empirical approximation given by Thomas and Bowman [1986].

• Solar radiation in wavelengths between 1 and 422.5 nm is considered, ionizing N2, O2, O, Ar, He, NO, O2(1g), CO2, and dissociating N2, O2, O3, H2O, H2O2, NO, NO2, HNO3 , and N2O5.

SIC model cont.



• The photoionization/dissociation cross sections as well as branching ratios for different products were gathered from various sources [Ohshio et al., 1966; McEwan and Phillips, 1975; Torr et al., 1979; Shimazaki, 1984;World Meteorological Organization, 1985; Rees, 1989; Fuller-Rowell, 1993; Minschwaner and Siskind, 1993; Siskind et al., 1995; Koppers and Murtagh, 1996; Sander et al., 2003].

• The numerous sources of reaction rate coefficients for the ionic reactions are listed in the work of Turunen et al. [1996] along with the additions listed in the work of Verronen et al. [2002].

SIC model cont.



• The negative ion chemistry scheme and the ion-ion recombination coefficient have been recently checked and revised according to and references in Kazil et al. [2003].

• The neutral chemistry includes 59 reactions of the modeled neutral species, for which the rate coefficients have been updated according to Sander et al. [2003].

• Most of these reactions are listed in the work of Verronen et al. [2002].

• Recent additions and changes are presented in Table 1 of Verronen et

al. [2005]

SIC model cont.



• The model includes a vertical transport code, described by Chabrillat et al. [2002], which takes into account molecular and eddy diffusion.

• Within the transport code the molecular diffusion coefficients are calculated according to Banks and Kockarts [1973].

• We use a fixed eddy diffusion coefficient profile, which has a maximum of

1.3 x 106 cm2 s -1 at 102 km.

• The SIC model can be run either in a steady-state or a time-dependent mode.

• Mostly we used the time-dependent mode which exploits the semi-implicit

Euler method for stiff sets of equations [Press et al., 1992], in order to advance the concentrations of the chemical species in time.

SIC model cont.



• Vertical transport and chemistry are advanced in 15-min intervals during which the background atmosphere and external forcing are kept constant.

• In the beginning of every interval all modeled neutrals, except the short-lived constituents O(1D) and N(2D), are transported.

• Next, new values for solar zenith angle, background atmosphere, and ionization/dissociation rates due to solar radiation and particle precipitation are calculated.

• Finally, the chemistry is advanced.

SIC model cont.



Ion reactions producing odd nitrogen



Problems

• Inputs for model work are not well known

– We need to know the energy and flux of the precipitating particles (solar origin/magnetospheric response)

– Details of many chemical processes are not known– Parametrizations and extrapolations are used in models

• We need more measurements

– Some key properties not measured at all from satellites– Measurements are often integrated averages– Simultaneous satellite and ground based measurements needed



Energy distribution of precipitating electrons

• Optical data combined with other data

– M. Ashrafi et al., Ann. Geoph., 2005• imaging riometer + all-sky optical data• DASI 557.7 nm + imaging riometer (+EISCAT calibration) -> energy

maps, assuming Maxwellian spectra• comparison with DMSP satellite data, conjugate passes

– H. Mori et al., Ann. Geoph., 2004• imaging riometer + meridian scanning photometer• ratio of 630.0 nm and 427.8 nm -> total flux + characteristic energy• Calculated CNA / observed CNA -> spectral shape

– M. Kosch et al., JGR, 2001• original work on energy maps using DASI and IRIS



Fig. 7 by Lummerzheim et al., 1990

• Empirical relationship I630.0 / I427.8 versus characteristic energy of the precipitating electrons



SGO all-sky camera, Feb 2006



Energy distribution of precipitating electrons

• We propose to combine standard optical data with:

– new digital ionosonde data with high dynamical range• E-region characteristics obtained even during auroral events• information on high-energy particles in the minimum frequency

– detailed ion-chemistry modeling• any assumed energy spectrum of precipitating particles can be used

as input• resulting electron density profile can be compared with ionosonde

data• high energy part can be compared with riometer data



SGO Alpha Wolf• SGO built a new CW FM chirp ionosonde in 2005

– 24 bit recording– 8 crossed loop antennae in receiver (20 units ready)– f=0.5-16 MHz– in operation since November, 2005



SGO Alpha Wolf• Extended sounding capability

– large dynamical range -> nearly continuous information of E-region characteristics even during auroral events

– soundings start at 0.5 MHz– fmin can be used to map high energy precipitation



Verronen et al., (2005)

NO produced by aurora



Electron precipitation



Electron precipitation

• Electron density as function of altitude at noon, without auroral activity during the previous night (blue) and with auroral activity during the previous night (red).



Afternoon absorption spike events

• Also isolated spikes found• Often extremely large

absorption values >5 dB,up to 15 dB

• Well-defined, confined region of absorption in IRIS field of view

• Example: IRIS beam 32 on 2002-10-27 at 1811 UT



Example:IRIS data

1995/11/01



IRIS data 2005/01/02



Relativistic electrons?

• Easy to produce high absorption by relativistic electron precipitation

• What is the flux?• Example: SAMPEX

data on four consecutive days in 1992, flux of electrons >400keV (precipitating fluxes)



What is the energy of the electrons?

• Foat et al. [GRL, 1998] report balloon observations of X-rays, consistent with precipitation of monoenergetic 1.7 MeV electrons, near Kiruna on Aug 20, 1996 at 1532 UT (L=5.8)

• Lorentzen et al. [JGR, 2000] give interpretation of this as a selective precipitation of ambient relativistic electrons from radiation belt



X ray spectraObserved in Kiruna,Aug 20, 1996at 1532 UT

Upper solid line:Model calculationfor 1.7 Mev electronsFitted to correctedspectrum

Lorentzen et al. [JGR, 2000]



Absorption seen by riometer



EISCAT observation of REPEISCAT VHF, GEN11, 1995/09/15

Power profile

Electron density

Electron density from fitted ISR D-region spectra show enhanced ionisation at 1310:



IRIS data 1995/09/15



Atmospheric effects of REP events

Ionisationrates:



Gaines et al. spectrum, 3 hrs

Responsein Ne

Assumeconstantionisationwith time,duration3 hours:




Responsein NO

Note:time axis startsat 12:00 andafter 24:00jumps to 00:00




Responsein O3




Responsein O3

Assumeconstantionisationwith time,duration24 hours:



Energy of the electrons from VLF data?

Model calculation:

Set up a constantionisation at allaltitudes, duration0.5 seconds.

Calculate the timedevelopment ofelectron densityafter the ionisationburst.



Energy of the electrons from relaxation?

Constant ionisation atall altitudes on for 0.5seconds:

Relaxation time ofthe elevated electrondensity is stronglydependent onaltitude.



Use decay time of a spike in data

Relaxation is a resultof several processeswhich have differentcharacteristic times.

Fitting a slow and fastexponential decay toSIC model results:

=>

At lower altitudes fastprocesses dominate.

At higher altitudes,there are only slowprocesses.



Electron penetration

altit

ude

[km

]

If REP microbursts would be nearly monoenergetic electrons, we could estimate the energy by fitting a model decay time to the observed decay in VLF data during a microburst.



VLF monitoring of precipitation



Actual VLF data

Sodankylä AARDDVARK receiver, 21 Jan 2005 (from C. Rodger et al., 2006)



Monoenergetic electrons

An example of decay due to a 0.1 s lasting ionisation by monoenergetic electrons of 1,2, and 3 MeV, shown together with experimental data from the Sodankylä AARDDVARK receiver (from C. Rodger et al., 2006)



Model of chorus-driven WEP

(model by Jacob Bortnik)



Monoenergetic electrons

Time varying electron number density calculated by the SIC model, showing the decay of a chorus-produced ionospheric change due to the model fluxes (left), and time varying VLF perturbation produced by the chorus-driven precipitation spectra (right), to be contrasted with the

observed FAST VLF perturbation (from C. Rodger et al., 2006)



Examples of REP bursts



Modelling a REP burst



• Assuming ≈1 MeV-energy particles:– Individual short duration burst have negligible effects

on neutrals– Repeated precipitation or duration in the order of 10

minutes may produce a few percent decrease in local ozone concentration

– Long-lasting events (days or more) can have significant effects even with low fluxes!!!

REP effect on neutrals



REP effects•There is a need to deduce precipitating electron characteristics

•Relativistic microbursts could be used together with chemistry modeling

•Multi-instrument approach is necessary - in addition to possible estimates from relaxation time:

•multiwavelenght all-sky imaging, high dynamic range ionosonde, with ion-chemical modeling, can be used•photometer data would be favoured•imaging riometer data should be added

•Ultimately X-ray satellite imaging needed



CMAT2: 3 D GCM



CMAT2: 3 D GCM• Citation: Dobbin, A. L. , A. D. Aylward, and M. J. Harris (2006 ), Three-

dimensional GCM modeling of nitric oxide in the lower thermosphere ,J. Geophys. Res. ,111 ,A07314 , doi: 10.1029/2005JA011543

• CMAT simulations suggest that under moderate geomagnetic conditions, the most equatorward geographic latitudes to be influenced by aurorally produced NO are 30°S and 45°N. Under conditions of high geomagnetic activity, aurorally produced NO is present at latitudes poleward of 15°S and 28°N.



SPE Oct 2003, GOMOS

From:A.Seppälä et al.(2006)



GOMOS, NO2

From:A.Seppälä et al.(2006)



How can IPY help?

•Solar proton precipitation at polar cap areas,•auroral electron precipitation at the auroral zone,•relativistic electron precipitation at auroral and sub-auroral latitudes,•variable cosmic ray ionisation,•solar extreme ultraviolet and X-radiation,

all are ionising energy inputs to the mesosphere and lower thermosphere (MLT). They all show large variations on different timescales, causing changes in the ion and neutral composition in the MLT region. During extreme ionisation events, direct effects in the stratosphere can be seen.



Thank you!

...work in progress....

Documents

The effect of high energy electron precipitation in MLT (Mesosphere-Lower Thermosphere)