Abstract
We have proposed a self-consistent picture of the sawtooth collapse according to which Kelvin-Helmholtz turbulence is responsible for rapid cross-field transport inside most of the hot spot. The K-H modes are driven by the sheared parallel flows which develop once localized sinks appear on the spot`s field lines. Localized and sudden sinking action is assumed to result from the enhancement of trapped electron mode turbulence/TEM outwards transport by large density and temperature gradients developing in the neigborhood of the X line; the latter are inherent to the transient magnetic configuration generated by the tearing precursor. The time-scales of the K-H dynamics are short compared to the collapse time: the tubulence level can then adjust instantaneously. TEM turbulence steeply decreases inwards of the X line; we have assumed, for convenience, that the sink, localized at the azimuthal angel(s) of the X point(s), decreases as r{sup 2}. The collapse mechanism does not concern the outer rim of the hot spot where the pitch of the helicoidal field lines is too close to unity and their period too large. This can be put in parallel with the observation that the sawtooth inversion radius is smaller than the radius of the q=1 magnetic surface
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Citation Formats
Rogister, A, and Ding, Li.
A mechanism for the sawtooth collapse.
Germany: N. p.,
1993.
Web.
Rogister, A, & Ding, Li.
A mechanism for the sawtooth collapse.
Germany.
Rogister, A, and Ding, Li.
1993.
"A mechanism for the sawtooth collapse."
Germany.
@misc{etde_10131463,
title = {A mechanism for the sawtooth collapse}
author = {Rogister, A, and Ding, Li}
abstractNote = {We have proposed a self-consistent picture of the sawtooth collapse according to which Kelvin-Helmholtz turbulence is responsible for rapid cross-field transport inside most of the hot spot. The K-H modes are driven by the sheared parallel flows which develop once localized sinks appear on the spot`s field lines. Localized and sudden sinking action is assumed to result from the enhancement of trapped electron mode turbulence/TEM outwards transport by large density and temperature gradients developing in the neigborhood of the X line; the latter are inherent to the transient magnetic configuration generated by the tearing precursor. The time-scales of the K-H dynamics are short compared to the collapse time: the tubulence level can then adjust instantaneously. TEM turbulence steeply decreases inwards of the X line; we have assumed, for convenience, that the sink, localized at the azimuthal angel(s) of the X point(s), decreases as r{sup 2}. The collapse mechanism does not concern the outer rim of the hot spot where the pitch of the helicoidal field lines is too close to unity and their period too large. This can be put in parallel with the observation that the sawtooth inversion radius is smaller than the radius of the q=1 magnetic surface (r{sub inv}/r{sub 1}{proportional_to}0.9 in TEXTOR). Cross-field and parallel transport are complementary; the latter vanishes on the spot`s magnetic axis ({rho}=0) and is maximum at the distance corresponding to the sawtooth inversion radius ({rho}=1), the divergence of the former is maximum at {rho}=0, decreases steadily outwards, vanishes for {rho}=1{radical}2, and has a negative minimum for {rho}=1. (orig.)}
place = {Germany}
year = {1993}
month = {Jul}
}
title = {A mechanism for the sawtooth collapse}
author = {Rogister, A, and Ding, Li}
abstractNote = {We have proposed a self-consistent picture of the sawtooth collapse according to which Kelvin-Helmholtz turbulence is responsible for rapid cross-field transport inside most of the hot spot. The K-H modes are driven by the sheared parallel flows which develop once localized sinks appear on the spot`s field lines. Localized and sudden sinking action is assumed to result from the enhancement of trapped electron mode turbulence/TEM outwards transport by large density and temperature gradients developing in the neigborhood of the X line; the latter are inherent to the transient magnetic configuration generated by the tearing precursor. The time-scales of the K-H dynamics are short compared to the collapse time: the tubulence level can then adjust instantaneously. TEM turbulence steeply decreases inwards of the X line; we have assumed, for convenience, that the sink, localized at the azimuthal angel(s) of the X point(s), decreases as r{sup 2}. The collapse mechanism does not concern the outer rim of the hot spot where the pitch of the helicoidal field lines is too close to unity and their period too large. This can be put in parallel with the observation that the sawtooth inversion radius is smaller than the radius of the q=1 magnetic surface (r{sub inv}/r{sub 1}{proportional_to}0.9 in TEXTOR). Cross-field and parallel transport are complementary; the latter vanishes on the spot`s magnetic axis ({rho}=0) and is maximum at the distance corresponding to the sawtooth inversion radius ({rho}=1), the divergence of the former is maximum at {rho}=0, decreases steadily outwards, vanishes for {rho}=1{radical}2, and has a negative minimum for {rho}=1. (orig.)}
place = {Germany}
year = {1993}
month = {Jul}
}