The ECOMA 2007 campaign: rocket observations and numerical modelling of aerosol particle charging and plasma depletion in a PMSE/NLC layer

Abstract. The ECOMA series of rocket payloads use a set of aerosol particle, plasma, and optical instruments to study the properties of aerosol particles and their interaction with the ambient plasma environment in the polar mesopause region. In August 2007 the ECOMA-3 payload was launched into a region with Polar Mesosphere Summer Echoes (PMSE) and noctilucent clouds (NLC). An electron depletion was detected in a broad region between 83 and 88 km, coincident with enhanced density of negatively charged aerosol particles. We also find evidence for positive ion depletion in the same region. Charge neutrality requires that a population of positively charged particles smaller than 2 nm and with a density of at least 2×108 m−3 must also have been present in the layer, undetected by the instruments. A numerical model for the charging of aerosol particles and their interaction with the ambient plasma is used to analyse the results, showing that high aerosol particle densities are required in order to explain the observed ion density depletion. The model also shows that a very high photoionisation rate is required for the particles smaller than 2 nm to become positively charged, indicating that these may have a lower work function than pure water ice.

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Identification and classification of the formation of intermediate ions measured in boreal forest

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-201-2007 ◽

2007 ◽

Vol 7 (1) ◽

pp. 201-210 ◽

Cited By ~ 92

Author(s):

A. Hirsikko ◽

T. Bergman ◽

L. Laakso ◽

M. Dal Maso ◽

I. Riipinen ◽

...

Keyword(s):

Boreal Forest ◽

Aerosol Particle ◽

Size Range ◽

Aerosol Particles ◽

Charged Particles ◽

Negative Ions ◽

Particle Formation ◽

Air Ions ◽

Charged Aerosol ◽

Positively Charged

Abstract. We have measured the size distributions of air ions (0.42–7.5 nm in diameter) with the Balanced Scanning Mobility Analyzer in boreal forest, in Southern Finland since spring 2003. The size range covers the size range of cluster ions (approximately 0.42–1.6 nm) and naturally charged nanometre aerosol particles (1.6–7.5 nm) or intermediate air ions. Based on the measurements from April 2003 to March 2006 we studied the characteristics of charged aerosol particle formation by classifying each day either as a particle formation event, undefined or non-event day. The principal of the classification, as well as the statistical description of the charged aerosol particle formation events are given. We found in total 270 (26% of the analysed days) and 226 (22% of the analysed days) particle formation days for negative and positive intermediate ions, respectively. For negatively charged particles we classified 411 (40% of the analysed days) undefined and 348 (34% of the analysed days) non-event days whereas for positively charged particles 343 (33% of the analysed days) undefined and 460 (45% of the analysed days) non-event days. The results were compared with the ordinary classification based on the Differential Mobility Particle Sizer (DMPS) measurements carried out at the same place. The above-presented values differed slightly from that found from the DMPS data, with a lower particle diameter of 3 nm. In addition, we have found the rain-induced intermediate ion bursts frequently. The rain effect was detected on 163 days by means of negative ions and on 105 days by positive ones. Another interesting phenomenon among the charged aerosol particles was the appearance and existence of intermediate ions during the snowfall. We observed this phenomenon 24 times with negatively charged particles and 21 times with positively charged ones during winter months (October–April). These intermediate air ions were seen during the snowfall and may be caused by ice crystals, although the origin of these intermediate ions is unclear at the moment.

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Charging of mesospheric aerosol particles: the role of photodetachment and photoionization from meteoric smoke and ice particles

Annales Geophysicae ◽

10.5194/angeo-27-2417-2009 ◽

2009 ◽

Vol 27 (6) ◽

pp. 2417-2422 ◽

Cited By ~ 35

Author(s):

M. Rapp

Keyword(s):

Electron Capture ◽

Aerosol Particles ◽

Pure Water ◽

Electron Attachment ◽

Water Ice ◽

Ice Particles ◽

Repeated Observation ◽

Meteoric Smoke ◽

Positively Charged

Abstract. Time constants for photodetachment, photoemission, and electron capture are considered for two classes of mesospheric aerosol particles, i.e., meteor smoke particles (MSPs) and pure water ice particles. Assuming that MSPs consist of metal oxides like Fe2O3 or SiO, we find that during daytime conditions photodetachment by solar photons is up to 4 orders of magnitude faster than electron attachment such that MSPs cannot be negatively charged in the presence of sunlight. Rather, even photoemission can compete with electron capture unless the electron density becomes very large (>>1000 cm−3) such that MSPs should either be positively charged or neutral in the case of large electron densities. For pure water ice particles, however, both photodetachment and photoemission are negligible due to the wavelength characteristics of its absorption cross section and because the flux of solar photons has already dropped significantly at such short wavelengths. This means that water ice particles should normally be negatively charged. Hence, our results can readily explain the repeated observation of the coexistence of positive and negative aerosol particles in the polar summer mesopause, i.e., small MSPs should be positively charged and ice particles should be negatively charged. These results have further important implications for our understanding of the nucleation of mesospheric ice particles as well as for the interpretation of incoherent scatter radar observations of MSPs.

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Identification and classification of the formation of intermediate ions measured in boreal forest

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-9187-2006 ◽

2006 ◽

Vol 6 (5) ◽

pp. 9187-9212

Author(s):

A. Hirsikko ◽

T. Bergman ◽

L. Laakso ◽

M. Dal Maso ◽

I. Riipinen ◽

...

Keyword(s):

Boreal Forest ◽

Aerosol Particle ◽

Size Range ◽

Aerosol Particles ◽

Charged Particles ◽

Negative Ions ◽

Particle Formation ◽

Air Ions ◽

Charged Aerosol ◽

Positively Charged

Abstract. We have measured the size distributions of air ions (0.42–7.5 nm in diameter) with the Balanced Scanning Mobility Analyzer in boreal forest, in Southern Finland since spring 2003. The size range covers the size range of cluster ions (approximately 0.42–1.6 nm) and naturally charged nanometre aerosol particles (1.6–7.5 nm) or intermediate air ions. Based on the measurements from April 2003 to March 2006 we studied the characteristics of charged aerosol particle formation by classifying each day either as a particle formation event, undefined or non-event day. The principal of the classification, as well as the statistical description of the charged aerosol particle formation events are given. We found in total 269 and 226 particle formation days for negative and positive intermediate ions, respectively. For negatively charged particles we classified 411 undefined and 349 non-event days whereas for positively charged particles 342 undefined and 461 non-event days. The results were compared with the ordinary classification based on Differential Mobility Particle Sizer (DMPS) measurements carried out at the same place. The above-presented values differed slightly from that found from the DMPS data, with a lower particle diameter of 3 nm. In addition, we have found the rain-induced intermediate ion bursts frequently. The rain effect was detected on 163 days by means of negative ions and on 104 days by positive ones. Another interesting phenomenon among the charged aerosol particles was the appearance and existence of intermediate ions during the snowfall. We observed this phenomenon 24 times with negatively charged particles and 21 times with positively charged ones during winter months (October–April). These intermediate air ions were seen during the snowfall and may be caused by ice crystals, although the origin of these intermediate ions is unclear at the moment.

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Study on the layered dusty plasma structures in the summer polar mesopause

Annales Geophysicae ◽

10.5194/angeo-28-1679-2010 ◽

2010 ◽

Vol 28 (9) ◽

pp. 1679-1686 ◽

Cited By ~ 3

Author(s):

◽

Keyword(s):

Density Distribution ◽

Gravity Wave ◽

Dusty Plasma ◽

Layer Structure ◽

Thin Layers ◽

Ion Density ◽

Ice Particles ◽

Summer Echoes ◽

Polar Mesosphere Summer Echoes ◽

Formation And Evolution

Abstract. Traditional hydrodynamic equations are adopted to build a one-dimensional theoretical model to study the effect of gravity wave on layered dusty plasma structures formation and evolution near the polar summer mesospause region associated with polar mesosphere summer echoes (PMSE). The proposed mechanism gives consideration to the charged ice particle motion by the gravity wave modulation, making a significant contribution to the vertical transport of heavy ice particles and convergence into thin layers. And numerical results show that the pattern of the multi-layer structure depends on the ration of the initial ice particles density distribution to the vertical wavelength of the gravity waves, the ice particle size and the wind velocity caused by gravity wave. Also, the variation of ion density distribution under the influence of gravity wave has also been examined. Finally, the electron density depletions (bite-outs) layers has been simulated according to the charge conservation laws, and the results are compared to the ECT02 rocket sounding data, which agree well with the measuring.

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Small scale plasma and charged aerosol variations and their importance for polar mesosphere summer echoes

Advances in Space Research ◽

10.1016/s0273-1177(99)00198-2 ◽

1999 ◽

Vol 24 (5) ◽

pp. 537-546 ◽

Cited By ~ 23

Author(s):

T.A. Blix

Keyword(s):

Small Scale ◽

Charged Aerosol ◽

Summer Echoes ◽

Polar Mesosphere Summer Echoes

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Evolution of Small Scale Density Perturbations of Plasma and Charged Aerosol Particles in Polar Mesospheric Summer Echoes (PMSE) Layers

Plasma Science and Technology ◽

10.1088/1009-0630/13/5/08 ◽

2011 ◽

Vol 13 (5) ◽

pp. 550-556

Author(s):

Zuquan Hu ◽

Yinhua Chen ◽

Jugao Zheng ◽

Hao Liu ◽

Mingyang Yu ◽

...

Keyword(s):

Aerosol Particles ◽

Small Scale ◽

Charged Aerosol ◽

Summer Echoes ◽

Density Perturbations

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Polar mesosphere summer echoes (PMSE): Review of observations and current understanding

Atmospheric Chemistry and Physics ◽

10.5194/acp-4-2601-2004 ◽

2004 ◽

Vol 4 (11/12) ◽

pp. 2601-2633 ◽

Cited By ~ 256

Author(s):

M. Rapp ◽

F.-J. Lübken

Keyword(s):

Electron Number Density ◽

Aerosol Particles ◽

Small Scale ◽

Number Density ◽

Electron Number ◽

Mesopause Region ◽

Air Turbulence ◽

Radar Echoes ◽

Summer Echoes ◽

Polar Mesosphere Summer Echoes

Abstract. Polar mesosphere summer echoes (PMSE) are very strong radar echoes primarily studied in the VHF wavelength range from altitudes close to the polar summer mesopause. Radar waves are scattered at irregularities in the radar refractive index which at mesopause altitudes is effectively determined by the electron number density. For efficient scatter, the electron number density must reveal structures at the radar half wavelength (Bragg condition for monostatic radars; ~3 m for typical VHF radars). The question how such small scale electron number density structures are created in the mesopause region has been a longstanding open scientific question for almost 30 years. This paper reviews experimental and theoretical milestones on the way to an advanced understanding of PMSE. Based on new experimental results from in situ observations with sounding rockets, ground based observations with radars and lidars, numerical simulations with microphysical models of the life cycle of mesospheric aerosol particles, and theoretical considerations regarding the diffusivity of electrons in the ice loaded complex plasma of the mesopause region, a consistent explanation for the generation of these radar echoes has been developed. The main idea is that mesospheric neutral air turbulence in combination with a significantly reduced electron diffusivity due to the presence of heavy charged ice aerosol particles (radii ~5–50 nm) leads to the creation of structures at spatial scales significantly smaller than the inner scale of the neutral gas turbulent velocity field itself. Importantly, owing to their very low diffusivity, the plasma structures acquire a very long lifetime, i.e., 10 min to hours in the presence of particles with radii between 10 and 50 nm. This leads to a temporal decoupling of active neutral air turbulence and the existence of small scale plasma structures and PMSE and thus readily explains observations proving the absence of neutral air turbulence at PMSE altitudes. With this explanation at hand, it becomes clear that PMSE are a suitable tool to permanently monitor the thermal and dynamical structure of the mesopause region allowing insights into important atmospheric key parameters like neutral temperatures, winds, gravity wave parameters, turbulence, solar cycle effects, and long term changes.

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Polar mesosphere summer echoes (PMSE): review of observations and current understanding

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-4-4777-2004 ◽

2004 ◽

Vol 4 (4) ◽

pp. 4777-4876 ◽

Cited By ~ 17

Author(s):

M. Rapp ◽

F.-J. Lübken

Keyword(s):

Electron Number Density ◽

Aerosol Particles ◽

Small Scale ◽

Number Density ◽

Electron Number ◽

Mesopause Region ◽

Air Turbulence ◽

Radar Echoes ◽

Summer Echoes ◽

Polar Mesosphere Summer Echoes

Abstract. Polar mesosphere summer echoes (PMSE) are very strong radar echoes primarily studied in the VHF wavelength range from altitudes close to the polar summer mesopause. Radar waves are scattered at irregularities in the radar refractive index which at mesopause altitudes is solely determined by the electron number density. For efficient scatter, the electron number density must reveal structures at the radar half wavelength (Bragg condition; ~3 m for typical VHF radars). The question how such small scale electron number density structures are created in the mesopause region has been a longstanding open scientific question for almost 30 years. This paper reviews experimental and theoretical milestones on the way to an advanced understanding of PMSE. Based on new experimental results from in situ observations with sounding rockets, ground based observations with radars and lidars, numerical simulations with microphysical models of the life cycle of mesospheric aerosol particles, and theoretical considerations regarding the diffusivity of electrons in the ice loaded complex plasma of the mesopause region, a consistent explanation for the generation of these radar echoes has been developed. The main idea is that mesospheric neutral air turbulence in combination with a significantly reduced electron diffusivity due to the presence of heavy charged ice aerosol particles (radii ~5–50 nm) leads to the creation of structures at spatial scales significantly smaller than the inner scale of the turbulent velocity field itself. Importantly, owing to their very low diffusivity, the plasma structures acquire a very long lifetime, i.e. 10 min to hours in the presence of particles with radii between 10 and 50 nm. This leads to a temporal decoupling of active neutral air turbulence and the existence of small scale plasma structures and PMSE and thus readily explains observations proving the absence of neutral air turbulence at PMSE altitudes. With this explanation at hand, it becomes clear that PMSE are a suitable tool to permanently monitor the thermal and dynamical structure of the mesopause region allowing insights into important atmospheric key parameters like temperatures, winds, gravity wave parameters, turbulence, solar cycle effects, and long term changes.

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